Double Doors

Moved the open door functionality to mixins.
^ This make it compatible with other mods such as FramedBlocks.
Fixed crouching not always ignoring the double door functionality.
Fixed the sound playing incorrectly for each trapdoor.
Fixed levers not opening double doors correctly.
Fixed buttons opening doors from too far away.

The complete changelog with previous versions can be found at:
  https://serilum.com/mods?changelog=double-doors