renamed OS-IDP spec file to OS-FEDERATION

This could have been done as part of a previous change [1] which
expanded the scope of the extension, but it made the diff in gerrit very
difficult to see additional changes. This is ONLY the file rename.

[1]: https://review.openstack.org/#/c/59848/

Change-Id: Ibce5940b61926028774f9c02e533d67ca958662f
Merge "renamed OS-IDP spec file to OS-FEDERATION"