Fences.

[MistakeNot4892]

Rewrites and expands on fences.

• Fences now autosmooth based on neighboring fences.
• Fences use the structure lock system (hence can have keys, be picked, etc.).
• Fences can be climbed again.
• Fences can do four and three way junctions.
• Log, brick, stick and plank fences have been added (thank you @PlayerDeer for the icons that I butchered)
• Fences can be constructed.

TODO

• Brick fence icons.
• Chain fence icons.
• Palisade icons.
• Plank fence icons.
• Stick fence icons.
• Convert locks to use structure logic.
• General icon pass to make sure they all smooth correctly.
• Testing.