Get 6.x-2.x branch of vcgit to a beta release

I'm using git backend while migrating to OOP, so it should be ready, at least one big part, after OOP is done.

More detail on versioncontrol_git github clone oop branch: http://github.com/marvil07/versioncontrol_git/tree/oop

first version of this now is available on HEAD(from my github oop branch), but vc api is in the process of define various aspects(see #595930: from github to d.o cvs(aka start 6.x-2.0-dev and get access)), so we depend on that

Need this for the phase 2 of the git migration, obviously

This is heading towards done, with some of the changes committed as part of the entities refactor and corni's refactor, though I'm gonna keep it open as the meta-issue for getting to a beta release.

VCS APi is still changing, but most of the big fat re-factor changes are already committed.

The only big changes pending I see in VCS API are:

- account re-factor, but hopefully is a minor change here.
- #879600: Meta: introduce an activity stream separate from commit logs, probably not impacting here.
- #879730: Replace the entire VersioncontrolOperation "subsystem" with VersioncontrolCommit, hopefully only function/method naming changes

What I am trying to say we should start a beta here only when VCS API have a beta at least(see #893012: [meta] Blockers to a 6.x-2.0 release)

Tagging Git Sprint 8

Release state not a launch blocker.

I will be using the same tag I used on versioncontrol project to track blockers here: versioncontrol-6.x-2.0-release-blocker.

We have a beta some time ago