First pass at bringing plfs.spec up to 2.4.

An rpm can be built with this spec file. However, we still need to
decide on what to do about VERSION and VERSION.LAYOUT. The spec file
currently has lines that work with these files commented out as cmake
doesn't do anything with them during a 'make install'. A changelog also
needs to be added.
Final edits to plfs.spec
Merge remote branch 'upstream/master'
Update release process with cmake steps.
Merge remote branch 'upstream/master'
Add comment about adding PLFS man pages to MANPATH.
Merge pull request #245 from dshrader/master

Update to plfs.spec, the release process, and letting users know about the default location of PLFS man pages