SLING-3286 - Remove plugin version overrides from poms

Remove most plugin version overrides. Still left in:

- a couple of projects where upgrading to the maven-bundle-plugins
  leads to errors (TODOs added)
- a couple of projects where the plugin version is newer than the
  one from the parent project ( comments added )

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1551060 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/pom.xml b/pom.xml
index 9a62e2c..a48a9f1 100644
--- a/pom.xml
+++ b/pom.xml
@@ -58,7 +58,6 @@
             <plugin>
                 <groupId>org.apache.felix</groupId>
                 <artifactId>maven-bundle-plugin</artifactId>
-                <version>2.3.7</version>
                 <extensions>true</extensions>
                 <configuration>
                     <instructions>