Add and commit initial file set when initializing a project

[mwvaughn]

The abaco init workflow sets up the project directory as a git repo as of CLI v1.3.0. This behavior will be extended by attempting to add and commit the initial file set to the git repository.

Other requirements:

• Process must be able to fail gracefully
• Users should be able to disable this (and subsequent) steps in the abaco init workflow on an ad hoc basis.
• Users should be able to set a global default for this behavior