123327 jkaabimofrad: RA-865: Added tests for upload content API to test "relativePath" multi-part field. Also, cleaned up MultiPartBuilder. git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/HEAD/root@126539 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261