cleaning up code and linking, sort of. #TrainsInMotion #Traincraft (1.7 rewrite)

- Removed a pointless rotation function.
- Removed a pointless check.
- Added some missing documentation (theres still more missing than I would like, 
I'll have to take a day sometime soon and just double check all my documentation).
- Linking now works, sometimes. Only works in 1 of the 4 circumstances.
Unlike the old way, in this way the trains and rollingstock maintain links to only 
the front and back linked rollingstock or trains and apply movement based on 
the distance from a pre-set linking point which is defined from the 
hitbox positions in front and back.
The method will need cleaning up and better compensation for different circumstances, 
but it's a really good starting point.
With any luck the first release for the 1.7 TC rewrite will be ready this month!
The work that's left aside from this little bit of linking isn't really things that 
make it difficult, it's just things there are a lot of, 
it will take time to get all that stuff setup, individual trans and rollingstock transferred, 
values converted by hand, new crafters made that support sorting, items, recipes, etc.