Plan for non-tile-based walking

It would be nice to (optionally) support non-tile-based walking

• Clean up wallmap checking code
  • Check additional collisions, for example, hitting the end of a wall that is perpendicular to you when you are not tile aligned
• Clean up NPC collision code
• Implement an optional non-aligned mode.
  • In non-aligned mode it should be possible to move in steps of any pixel-size.
  • Explore the possibility of a half-aligned mode similar to the half-tile steps in the original NES zelda.
  • Some RPGs implement "sliding" when you collide with a wall close to a corner. Should we attempt to implement this?
  • In non-aligned mode, NPC activation behavior might have to change

There may be other complications I haven't thought of yet here.

Side Scrollers

A nice side-effect of this plan is that it will make it easier for plotscripters to make Side scrolling games without needing to re-implement their own hit-detection.