Restructuring of app.py

[LucasCampos]

I have to preface this saying that the design of vb_tool was never great to start with. I think that now that we are about to add another mode, hybrid searchlight (check pull #31), we really have to reconsider our approach. My main issue is that there are far too many flags that depend on the specific mode, which can be super confusing.

I propose the following new design:

• Each mode will have its own entry point (vb_searchlight, vb_fullbrain, etc)
• The existing vb_tool would print a help message explaining the various entry points
  • A second idea is that we could have something like vb_tool [tool] --flag1 --flag2 (...). I am still in favour of the first one, though.

This would, of course, break backwards compatibility.

Do you think this is a good approach?

[claudebajada]

I agree ... tend to think option 2 would be optimal.... But happy to discuss. We may also want to scrap the purely surface based approachs if we don't think they give optimal results.

Though I think we should still push the current hybrid approach first and then start thinking about major overhaul later.

On a related note, we need to think about how the GUI can cope with these changes.