Fixes buildout.cfg sample to include pygit2 in openerp env + increments pygit version just in case.
Removes url field.
Prepares commit update/delete mechanisms.
Renames git_repositories osv object to git_repository + fixes programming error.
Adds commit object model and view.
Renames view repositories records to 'repository'.
Adds repo_id key to 'commit' model + makes the update/delete commits mechanisms work.
Renames 'update_' method to 'add_' that it is at the end.