Towards supporting Git based projects

AlitheiaCore already supports SVN-based projects. The fundamental difference between SVN and Git is that in Git a revision can have many parent revisions. It seems that the database schema can accommodate this characteristic of Git by design.

Specifically, AlitheiaCore's programming model and the respective database model seem to be in good shape in order to support many parents per revision. Parent - child revision pairs are stored in an extra database table.