fix relativePath to plugins parent and bump to latest parent for all plugins

git-svn-id: https://svn.apache.org/repos/asf/maven/plugins/trunk@1082832 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/pom.xml b/pom.xml
index 353afae..30b60fe 100644
--- a/pom.xml
+++ b/pom.xml
@@ -25,7 +25,8 @@
   <parent>
     <artifactId>maven-plugins</artifactId>
     <groupId>org.apache.maven.plugins</groupId>
-    <version>18</version>
+    <version>19</version>
+    <relativePath>../maven-plugins/pom.xml</relativePath>
   </parent>
 
   <artifactId>maven-changelog-plugin</artifactId>