Fast forwarding / backwards. Breakable objects.

Changelog:
 1. Level switching:
  - Only works with non-State levels.
  - Due to the particularity of State levels, I decided not to implement
    it. Both because it's a pain in the ass due to having to check a lot
    of stuff for just deciding whether it's a non-State or not and also
    since all of this is just debug features. It's really not essential.
  - To fast forward press: ']'
  - To go backwards press: '['
 2. Breakable objects:
  - They should now be generic.
  - A template: BreakableObject is used.
  - When a 'breakable' Object is detected, it searches for its 'type'
    property. It then appends its type to the "Breakable" string. Thus, if
    you wish to create a BreakablePlatform, add a "Platform" value to its
    'type' key property.
  - I don't have any art on BreakableWalls or Doors yet, but once I have
    them I'll test whether it actually works.

Tick list:
 - I'm ticking from my list the following:
  I. Destructible walls and doors
   o Partially, since it still needs testing.
  V. Debug tools. Fast forward a level. Backwards a level.

Woo! End of File!