Comfortable, Mouse-Only Tile Editing

[caiolopez]

Problem:

• Having to constantly switch between brush and eraser can be tiresome, if not detrimental for hand-disabled users.
• It would be great to have a way to delete tiles while still in brush mode -- most pixel editing apps will feature a right-click or middle-click to erase, for instance.

Suggestion 1:

• Make a checkbox on preferences that makes the wheel-click delete tile/object instead of "HAND" tool.
  This way, most users will keep working the way it is, while disabled and other users can maximize their productivity.

Suggestion 2:

• Make it so that selecting an empty tile lets me place that empty tile over used tiles, effectively deleting it.
  This idea won't truly solve the problem but mitigate it. I would suggest implementing both.