Update site menu for the modules.

- Add release 1.3 javadoc link
- Fix relative path for the top right banner image and link

Clarify release notes on where to update the site.xml.
diff --git a/commons-rng-client-api/src/site/site.xml b/commons-rng-client-api/src/site/site.xml
index dea235e..ea0e6cf 100644
--- a/commons-rng-client-api/src/site/site.xml
+++ b/commons-rng-client-api/src/site/site.xml
@@ -18,8 +18,8 @@
 <project name="RNG">
   <bannerRight>
     <name>Apache Commons RNG</name>
-    <src>/images/commons_rng.small.png</src>
-    <href>/index.html</href>
+    <src>../images/commons_rng.small.png</src>
+    <href>../index.html</href>
   </bannerRight>
 
   <body>
@@ -27,6 +27,8 @@
       <item name="Overview" href="index.html"/>
       <item name="Latest API docs (development)"
             href="apidocs/index.html"/>
+      <item name="Javadoc (1.3 release)"
+            href="https://commons.apache.org/rng/commons-rng-client-api/javadocs/api-1.3/index.html"/>
       <item name="Javadoc (1.2 release)"
             href="https://commons.apache.org/rng/commons-rng-client-api/javadocs/api-1.2/index.html"/>
       <item name="Javadoc (1.1 release)"
diff --git a/commons-rng-core/src/site/site.xml b/commons-rng-core/src/site/site.xml
index c3ae3d7..86e0837 100644
--- a/commons-rng-core/src/site/site.xml
+++ b/commons-rng-core/src/site/site.xml
@@ -18,8 +18,8 @@
 <project name="RNG">
   <bannerRight>
     <name>Apache Commons RNG</name>
-    <src>/images/commons_rng.small.png</src>
-    <href>/index.html</href>
+    <src>../images/commons_rng.small.png</src>
+    <href>../index.html</href>
   </bannerRight>
 
   <body>
@@ -27,6 +27,8 @@
       <item name="Overview" href="index.html"/>
       <item name="Latest API docs (development)"
             href="apidocs/index.html"/>
+      <item name="Javadoc (1.3 release)"
+            href="https://commons.apache.org/rng/commons-rng-core/javadocs/api-1.3/index.html"/>
       <item name="Javadoc (1.2 release)"
             href="https://commons.apache.org/rng/commons-rng-core/javadocs/api-1.2/index.html"/>
       <item name="Javadoc (1.1 release)"
diff --git a/commons-rng-sampling/src/site/site.xml b/commons-rng-sampling/src/site/site.xml
index a33ce05..8c98633 100644
--- a/commons-rng-sampling/src/site/site.xml
+++ b/commons-rng-sampling/src/site/site.xml
@@ -18,8 +18,8 @@
 <project name="RNG">
   <bannerRight>
     <name>Apache Commons RNG</name>
-    <src>/images/commons_rng.small.png</src>
-    <href>/index.html</href>
+    <src>../images/commons_rng.small.png</src>
+    <href>../index.html</href>
   </bannerRight>
 
   <body>
@@ -27,6 +27,8 @@
       <item name="Overview" href="index.html"/>
       <item name="Latest API docs (development)"
             href="apidocs/index.html"/>
+      <item name="Javadoc (1.3 release)"
+            href="https://commons.apache.org/rng/commons-rng-sampling/javadocs/api-1.3/index.html"/>
       <item name="Javadoc (1.2 release)"
             href="https://commons.apache.org/rng/commons-rng-sampling/javadocs/api-1.2/index.html"/>
       <item name="Javadoc (1.1 release)"
diff --git a/commons-rng-simple/src/site/site.xml b/commons-rng-simple/src/site/site.xml
index 00bd879..0a5230e 100644
--- a/commons-rng-simple/src/site/site.xml
+++ b/commons-rng-simple/src/site/site.xml
@@ -18,8 +18,8 @@
 <project name="RNG">
   <bannerRight>
     <name>Apache Commons RNG</name>
-    <src>/images/commons_rng.small.png</src>
-    <href>/index.html</href>
+    <src>../images/commons_rng.small.png</src>
+    <href>../index.html</href>
   </bannerRight>
 
   <body>
@@ -27,6 +27,8 @@
       <item name="Overview" href="index.html"/>
       <item name="Latest API docs (development)"
             href="apidocs/index.html"/>
+      <item name="Javadoc (1.3 release)"
+            href="https://commons.apache.org/rng/commons-rng-simple/javadocs/api-1.3/index.html"/>
       <item name="Javadoc (1.2 release)"
             href="https://commons.apache.org/rng/commons-rng-simple/javadocs/api-1.2/index.html"/>
       <item name="Javadoc (1.1 release)"
diff --git a/doc/release/release.howto.txt b/doc/release/release.howto.txt
index 9a7578e..76c5906 100644
--- a/doc/release/release.howto.txt
+++ b/doc/release/release.howto.txt
@@ -181,7 +181,8 @@
 
 In particular:
  * Update and commit the "src/site/site.xml" file to contain the information
-   about the API docs of the new release.
+   about the API docs of the new release. This is for each of
+   common-rng-<module> with <module>: client-api; core; sampling; and simple.
  * Estimate a release date (taking into account the release vote delay) and
    insert it in the "src/changes/changes.xml" file.
  * Update the "pom.xml" to contain the final version number and not a SNAPSHOT: