Merge pull request #163 from skyboy/original

Fix reversed direction mappings.
Fix deathrat's typos
Fix #166
Fixes #165
Closes #164 - decorative blocks as facades
Fix #160 - autospawner slot filter
Added schmitt trigger circuit
New circuits start with input as CNST 0
Conveyors properly slope into psuedo-solid blocks
Merge remote-tracking branch 'upstream/master'