[UIMA-4094][UIMA-4095] Fixes to indexes, also switching to PostiveIntSet impl for bag indexes.  Add also new test cases. Update Javadocs to clarify that moveTo(fs) where fs is beyond the end, gives an isValid() == false result.

git-svn-id: https://svn.apache.org/repos/asf/uima/uimaj/trunk@1637457 13f79535-47bb-0310-9956-ffa450edef68
[UIMA-4096] update enforcer plugin config to spec Java 7 for UIMAJ

git-svn-id: https://svn.apache.org/repos/asf/uima/uimaj/trunk@1637463 13f79535-47bb-0310-9956-ffa450edef68