Expand Screen Event Handling

Lots of bugs in chat room maps currently arise because it registers it's own events. To solve these issues in the future, additional functionalities for screens to handle mouse and key events need to be introduced.

This MR adds support to handle the following events in game screens:

• MouseDown
• MouseUp
• MouseMove
• MouseWheel
• KeyUp

The MouseDown, MouseUp and MouseMove events also trigger with the corrosponding touch events on mobile.

In addition to this, the MouseClick event logic has been slightly altered to use the underlying mousedown and mouseup events. This is necessary because JS doesn't seem to throw native click events when the other two are used. The behaviour in the game, however, is completely the same.

In addition to this, the logic of KeyDown has been altered, so the events are forwarded to the active screen as long as they are not used somewhere else (in the struggle minigame, for example).