fixes #1995
added test for https://github.com/RestKit/RestKit/issues/2000
Merge pull request #1996 from valeriomazzeo/1995-localObjectsFromFetchRequests

fixes #1995 - RKMananagedObjectRequestOperation:localObjectsFromFetchRequests parameter not used
fixes #2000
better fix for #2000 #2001 #1990
Merge pull request #2001 from valeriomazzeo/2000-string-identifier

fixes #2000 #1990