[MGit] Provide a command line area to execute git commands

**Note:** Issue created after app developer's response to Google play review. > The app is great for straightforward editing on the go. The one thing it's lacking is a commandline area where git commands can be executed. Just yesterday I was in need of rolling back the last commit after accidentally commiting it to the master branch instead of a feature branch. While the command to do so is straightforward, it is not possible with the app in its current state. I'll happily change my rating to 5 stars if the ability to execute git commands is implemented.