ISPN-3242 Enforce building against JDK7 but verify that we are compatible with JDK6. Run testsuite against JDK6 if the JAVA_HOME_16 environment variable is set
ISPN-3284 Drop useless dependencies which we had to keep around because of http://bugs.sun.com/view_bug.do?bug_id=6550655

Other minor pom cleanups