Prevent snapping fixes

[meronz]

I tested the features introduced in PR #79 and found a few issues.

• The feature did not work when tabs were enabled. I made it work using the same technique used by USE_MODIFIER
• The helping overlay did not show again when the SUPER key was released after it being pressed.
• I made the PREVENT_SNAPPING setting mutually exclusive with USE_MODIFIER, since it is not useful to support them both at the same time.

@asteinba could you test these fixes and provide feedback? I think that everything should work fine as I tested all the combinations possible (tabs/no tabs, multiple zones/no multiple zones, etc.).

[meronz]

I'm going to merge this anyway since it is working for me. Let me know if there are any issues, so that i can hotfix them!