Replacing egdist with gitdist (TriBITS #15)

As I will be removing the dependence of checkin-test.py on eg and instead use
git directly, I also wanted to remove the usage of egdist and replace it with
gitdist.  gitdist does not even mention eg and uses .gitdist instead of
.egdist.

I have added deprecated warnings to egdist and have removed its unit tests.  I
will not be maintaining egdist any further.

Build/Test Cases Summary
Enabled Packages: TriBITS
Enabled all Forward Packages
0) MPI_DEBUG => passed: passed=139,notpassed=0 (0.69 min)
1) SERIAL_RELEASE => passed: passed=139,notpassed=0 (0.57 min)
Switching from egdist to gitdist (TriBITS #15)
Merge remote branch 'casl-dev/master'