Initial touch support

[nk-coding]

Adds initial touch support

• TouchTool similar to MouseTool
• Touch support for canvas scroll / zoom

Open questions

• I did not yet add the IMouseListener as discussed in Mobile / touch support #462
  • If you want I can do so, however this would likely result in a breaking change, as I would need to change the signature of MouseTool
• I added no decorate method to ITouchListener, as if the TouchTool would call it an a class both extends MouseListener and ITouchListener, it would be called twice
  • I could add it and only call it if the ITouchListener is not a MouseListener, however this sounds hacky
• I slightly changed the signature of some of the methods of ScrollMouseListener (e.g. moveScrollBar) to also accept a Touch as the event (as this provides the touch coordinates similar to the MouseEvent
  • technically, this is a breaking change
  • alternative options: implement touch scroll in separete class (and duplicate some code)
  • add new internal methods to ScrollMouseListener which basically are the current ones with the new signature, and make the current one call these new ones
• Currently, there is no touch support for moving elements
  • thus, currently the canvas scroll works even when touching a movable element
  • I can add support for moving elements, however I'm not sure if this is even desired
  • the point above (minor breaking changes vs duplicate code or internal wrapper method) applies here too

Closes #462

[spoenemann]

Great contribution, thanks a lot!

There are a few linter errors, please have a look.

I think it's ok to handle the interface extraction from MouseListener separately. Could you create a new issue for that and described the necessary steps to clean up the code?

One thing I noticed on my MacBook is that the pinch gesture for zooming feels a bit slow.