Sable Trees/Dynamic Trees Compatibility

0.8.0

• 3x3 trunks get one wide notch. 
• Roots hold the tree: A 3x3 trunk with surface roots around its base can't be notched at the base until the roots are cut.
  
  Fixes
  - Fixed: The underside of the trunk right above a notch was see-through, on every tree.
  - Fixed: the underside of fallen 3x3 trunks was see-through.
  - Fixed: breaking or hitting 3x3 trunks made missing-texture (purple and black) particles.
  - Fixed: fallen 3x3 trunks and some thin trunk pieces sank into the ground.
  - Fixed: branches on thick trees (big birches, for example) stayed floating next to the trunk after their connection was cut, both on standing and on fallen trees.
  - Fixed: the underside of the trunk just above a notch was see-through, and thick birches showed a gap between the notch and the trunk above.
  
  Know Issues
  - Sometimes a gap shows in the trunk right above a notch.