Add support for <item> elements defined in dimens

This is fix for issue #977.
PackageResourceLoader did not collect <item> elements defined in resource. The pull request constains small fix to force collecting those elements.
I have add also two tests to check collecting dimens defined by <dimen> tag and defined by <item> tag.

Tests report:
Results :
Tests run: 2326, Failures: 0, Errors: 0, Skipped: 61

mvn clean install result:
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2:39.567s
[INFO] Finished at: Fri Feb 28 16:34:00 CET 2014
[INFO] Final Memory: 36M/380M
[INFO] ------------------------------------------------------------------------