Add support for git-hooks

[jasny]

Git hooks is a tool to manage git hooks.

DBVC should be able to install simple by running

dbvc install-hooks [--path=...] [status] [mark]

The command should check if git-hooks is installed on the system. If not, give a message that you need to install git-hooks in order to use this feature.

I should also check if git-hooks is enabled for this project. If not message that you need to run git hooks install.

Specifying a path is optional. By default use the .githooks directory.

If you don't specify which hook(s) to install, install both hooks.

status

The status hook should simply run git status -q after a merge.

mark

The mark hook should run after a commit. It should mark the updates of that commit (only) as done. (see #6)