Refactored, changed store to sqlite and added git branch/top-level support

[Edke]

Hi again.

For now this suits my idea about this tool should work. There are some functionalities that I didnt port to my version as they become obsolte with these changes. Please feel free to test and comment. If you will be willing to merge somehow, we can find optimal balance with new features against legacy functionality and then we can create new version together that can be used as proper upgrade on pypi repo.