Improve settings management

[galindus]

Hi I have done some more modifications, in addition to Fix #11. I have added file settings so users can modify setting easily and to allow more file extensions. I have added menu captions so it can be done directly from sublime menus and added a caption to run the command too.

I think error messages should appear in dialog boxes. I will add that too in a later commit.

Hope it helps.

\BR