Add a lighter-but-slower Cython-based gcoder Line implementation
Rewrite gcoder_line to use properties instead of hacking setattr
Mostly revert 099c68ef89 as we can do it in a cleaner way now
Don't mark GLine hidden members as public
Use a single array of bits to store None/non-None status
Reuse bitarray for boolean properties
Merge branch 'experimental' of github.com:kliment/Printrun into experimental