Zoom and padding should be improved

[wokste]

The sub-issues are:

• [x] Zoom should use the mouse coordinates
• [x] Padding should use the zoom level.
• [x] Resize screen should keep the current zoom level
• [x] Selecting tiles won't work when zoomed.

These issues should be solved simultaneously.

[wokste]

Closing this but I have an error in #16 which currently prevents optimal usage