[ofiwg] merge of libfabric and fabtests git repo's

[Hefty, Sean]

The fabtests master branch has been merged into the libfabric master branch.  All future changes to fabtests should target the libfabric/fabtests directory.  The fabtests master branch will be frozen.

Libfabric and fabtests will maintain separate build files, with separate packages being generated.

The existing stable branches (v1.6.x and prior) for fabtests will remain where they are, and can continue to be updated with fixes.  Future stable branches (v1.7.x and later) will be part of the libfabric repo.

- Sean