Build messagefacility module using subtree structure

Update paths in messagefacility_module.cmake script to reflect new
subtree structure. Add resultant OBJECT library into FNALCore build,
and add include paths to INTERFACE definitions.

No tests are yet implemented for messagefacility as their structure
under the subtree is complex, with possibly obsolete tests.

NB: Build has not been verified in this commit because of errors
in building with Clang on OSX Mavericks:

- messagefacility/MessageService/ELtsErrorLog.icc causes issues
due to returns and protected visibility.

May work on FNAL gcc platforms...