Add a new TonelLoaderGitParentBaseEditionStrategy about tonel-vast

[eMaringolo]

We discussed this in a meeting with Mariano, and what we want is an option to load a base edition of an Application/Subapplication that is closer to what was versioned instead of using the latest one.

E.g. You're loading YourApplication from Tonel sources in a git repository, and the git HEAD is at the cf1234ab commit hash, and its parent commit is e2394a92, then when looking for a base edition to load, we look for one that matches such commit hash (by means of a pattern, text-search, etc.), so we find YourApplication master-e2394a92 edition and load that instead of the "latest one" (which in some cases might be the same one).

[eMaringolo]

After looking and reading about the internals of git, there is no simple way to extract the parent commits of a particular commit other than to parse directly the binary files in .git/objects/, in some cases requiring to parse the packfiles.

We would need to extract the commit by calling a git command on the git repository.

So:

$ git cat-file commit HEAD
tree 47b9dc8f9e2cc5da2c09aebf79731e6f35fa7d85
parent c3b72568c09808a298280800c38ba14e0a1c8414
author Esteban A. Maringolo  1577745693 -0300