EHN: Add auto recover support for incremental patching.

In the event like machine shutting down, the incremental patching process
might fail. If auto_recover option is enabled, re-run the patching process
will then query the lastest patch installed in the specified running VistA
instance, restore the cache.dat corresponding to the patch from backup
location based on the commit message and git hash in VistA-M repository.

GitUtils:
 Add a function to retrieve last commit information like timestamp, commit
 message, and hash from a git repository.

VistAPackageInfoFetcher:
 Add methods to query all the patches that are installed after specified
 timestamp based on either package file or install file, also add
 corresponding tests.

OSEHRA-Id: http://issues.osehra.org/browse/VAF-137
Change-Id: I590785581c4c795d442a26c5e99a9e3800e8715c