INT-2468 - Fix DocBook <ulink/> PDF Problems

* upgrade the Docbook Reference plugin dependency from version **0.1.2-SNAPSHOT** to **0.1.3**
* change any occurrences (only the external links):

from

    <link href="http://www.eaipatterns.com/StoreInLibrary.html">Claim Check</link>

to

    <ulink url="http://www.eaipatterns.com/StoreInLibrary.html">Claim Check</ulink>

build.gradle

@@ -9,7 +9,7 @@ buildscript {
     }
     dependencies {
         classpath 'org.springframework.build.gradle:bundlor-plugin:0.1.2-SNAPSHOT'
-        classpath 'org.springframework.build.gradle:docbook-reference-plugin:0.1.2-SNAPSHOT'
+        classpath 'org.springframework.build.gradle:docbook-reference-plugin:0.1.3'
     }
 }