Update Dockerfiles for 1.12.1 release

This closes #56
diff --git a/1.12/scala_2.11-java11-debian/Dockerfile b/1.12/scala_2.11-java11-debian/Dockerfile
index 50c635e..9b393e2 100644
--- a/1.12/scala_2.11-java11-debian/Dockerfile
+++ b/1.12/scala_2.11-java11-debian/Dockerfile
@@ -44,9 +44,9 @@
   gosu nobody true
 
 # Configure Flink version
-ENV FLINK_TGZ_URL=https://www.apache.org/dyn/closer.cgi?action=download&filename=flink/flink-1.12.0/flink-1.12.0-bin-scala_2.11.tgz \
-    FLINK_ASC_URL=https://www.apache.org/dist/flink/flink-1.12.0/flink-1.12.0-bin-scala_2.11.tgz.asc \
-    GPG_KEY=D9839159 \
+ENV FLINK_TGZ_URL=https://www.apache.org/dyn/closer.cgi?action=download&filename=flink/flink-1.12.1/flink-1.12.1-bin-scala_2.11.tgz \
+    FLINK_ASC_URL=https://www.apache.org/dist/flink/flink-1.12.1/flink-1.12.1-bin-scala_2.11.tgz.asc \
+    GPG_KEY=F8E419AA0B60C28879E876859DFF40967ABFC5A4 \
     CHECK_GPG=true
 
 # Prepare environment
diff --git a/1.12/scala_2.11-java11-debian/release.metadata b/1.12/scala_2.11-java11-debian/release.metadata
index b02dcab..901a0a7 100644
--- a/1.12/scala_2.11-java11-debian/release.metadata
+++ b/1.12/scala_2.11-java11-debian/release.metadata
@@ -1,2 +1,2 @@
-Tags: 1.12.0-scala_2.11-java11, 1.12-scala_2.11-java11, scala_2.11-java11
+Tags: 1.12.1-scala_2.11-java11, 1.12-scala_2.11-java11, scala_2.11-java11
 Architectures: amd64
diff --git a/1.12/scala_2.11-java8-debian/Dockerfile b/1.12/scala_2.11-java8-debian/Dockerfile
index 4d3b0f2..2ed4085 100644
--- a/1.12/scala_2.11-java8-debian/Dockerfile
+++ b/1.12/scala_2.11-java8-debian/Dockerfile
@@ -44,9 +44,9 @@
   gosu nobody true
 
 # Configure Flink version
-ENV FLINK_TGZ_URL=https://www.apache.org/dyn/closer.cgi?action=download&filename=flink/flink-1.12.0/flink-1.12.0-bin-scala_2.11.tgz \
-    FLINK_ASC_URL=https://www.apache.org/dist/flink/flink-1.12.0/flink-1.12.0-bin-scala_2.11.tgz.asc \
-    GPG_KEY=D9839159 \
+ENV FLINK_TGZ_URL=https://www.apache.org/dyn/closer.cgi?action=download&filename=flink/flink-1.12.1/flink-1.12.1-bin-scala_2.11.tgz \
+    FLINK_ASC_URL=https://www.apache.org/dist/flink/flink-1.12.1/flink-1.12.1-bin-scala_2.11.tgz.asc \
+    GPG_KEY=F8E419AA0B60C28879E876859DFF40967ABFC5A4 \
     CHECK_GPG=true
 
 # Prepare environment
diff --git a/1.12/scala_2.11-java8-debian/release.metadata b/1.12/scala_2.11-java8-debian/release.metadata
index 3e3769f..c8cd682 100644
--- a/1.12/scala_2.11-java8-debian/release.metadata
+++ b/1.12/scala_2.11-java8-debian/release.metadata
@@ -1,2 +1,2 @@
-Tags: 1.12.0-scala_2.11-java8, 1.12-scala_2.11-java8, scala_2.11-java8, 1.12.0-scala_2.11, 1.12-scala_2.11, scala_2.11
+Tags: 1.12.1-scala_2.11-java8, 1.12-scala_2.11-java8, scala_2.11-java8, 1.12.1-scala_2.11, 1.12-scala_2.11, scala_2.11
 Architectures: amd64
diff --git a/1.12/scala_2.12-java11-debian/Dockerfile b/1.12/scala_2.12-java11-debian/Dockerfile
index 48c2b59..c1e11b8 100644
--- a/1.12/scala_2.12-java11-debian/Dockerfile
+++ b/1.12/scala_2.12-java11-debian/Dockerfile
@@ -44,9 +44,9 @@
   gosu nobody true
 
 # Configure Flink version
-ENV FLINK_TGZ_URL=https://www.apache.org/dyn/closer.cgi?action=download&filename=flink/flink-1.12.0/flink-1.12.0-bin-scala_2.12.tgz \
-    FLINK_ASC_URL=https://www.apache.org/dist/flink/flink-1.12.0/flink-1.12.0-bin-scala_2.12.tgz.asc \
-    GPG_KEY=D9839159 \
+ENV FLINK_TGZ_URL=https://www.apache.org/dyn/closer.cgi?action=download&filename=flink/flink-1.12.1/flink-1.12.1-bin-scala_2.12.tgz \
+    FLINK_ASC_URL=https://www.apache.org/dist/flink/flink-1.12.1/flink-1.12.1-bin-scala_2.12.tgz.asc \
+    GPG_KEY=F8E419AA0B60C28879E876859DFF40967ABFC5A4 \
     CHECK_GPG=true
 
 # Prepare environment
diff --git a/1.12/scala_2.12-java11-debian/release.metadata b/1.12/scala_2.12-java11-debian/release.metadata
index 234cbda..3a8ffce 100644
--- a/1.12/scala_2.12-java11-debian/release.metadata
+++ b/1.12/scala_2.12-java11-debian/release.metadata
@@ -1,2 +1,2 @@
-Tags: 1.12.0-scala_2.12-java11, 1.12-scala_2.12-java11, scala_2.12-java11, 1.12.0-java11, 1.12-java11, java11
+Tags: 1.12.1-scala_2.12-java11, 1.12-scala_2.12-java11, scala_2.12-java11, 1.12.1-java11, 1.12-java11, java11
 Architectures: amd64
diff --git a/1.12/scala_2.12-java8-debian/Dockerfile b/1.12/scala_2.12-java8-debian/Dockerfile
index ceb8bb1..777abda 100644
--- a/1.12/scala_2.12-java8-debian/Dockerfile
+++ b/1.12/scala_2.12-java8-debian/Dockerfile
@@ -44,9 +44,9 @@
   gosu nobody true
 
 # Configure Flink version
-ENV FLINK_TGZ_URL=https://www.apache.org/dyn/closer.cgi?action=download&filename=flink/flink-1.12.0/flink-1.12.0-bin-scala_2.12.tgz \
-    FLINK_ASC_URL=https://www.apache.org/dist/flink/flink-1.12.0/flink-1.12.0-bin-scala_2.12.tgz.asc \
-    GPG_KEY=D9839159 \
+ENV FLINK_TGZ_URL=https://www.apache.org/dyn/closer.cgi?action=download&filename=flink/flink-1.12.1/flink-1.12.1-bin-scala_2.12.tgz \
+    FLINK_ASC_URL=https://www.apache.org/dist/flink/flink-1.12.1/flink-1.12.1-bin-scala_2.12.tgz.asc \
+    GPG_KEY=F8E419AA0B60C28879E876859DFF40967ABFC5A4 \
     CHECK_GPG=true
 
 # Prepare environment
diff --git a/1.12/scala_2.12-java8-debian/release.metadata b/1.12/scala_2.12-java8-debian/release.metadata
index bb3d3af..5fc3af7 100644
--- a/1.12/scala_2.12-java8-debian/release.metadata
+++ b/1.12/scala_2.12-java8-debian/release.metadata
@@ -1,2 +1,2 @@
-Tags: 1.12.0-scala_2.12-java8, 1.12-scala_2.12-java8, scala_2.12-java8, 1.12.0-scala_2.12, 1.12-scala_2.12, scala_2.12, 1.12.0-java8, 1.12-java8, java8, 1.12.0, 1.12, latest
+Tags: 1.12.1-scala_2.12-java8, 1.12-scala_2.12-java8, scala_2.12-java8, 1.12.1-scala_2.12, 1.12-scala_2.12, scala_2.12, 1.12.1-java8, 1.12-java8, java8, 1.12.1, 1.12, latest
 Architectures: amd64