The start of linking, and some bumps in the road. #TrainsInMotion (and the 1.7 TC rewrite)

- rollingstock can now be pushed.
- Fixed some useless checks with the movement code in trains.
- Added some notes on how to handle connecting trains and rollingstock since that will be the next goal after a hitbox rework.

The bump in the road is that the collision detection isn't very reliable when it comes to tests for if the player is trying to push the rollingstock. I think I will need to rework a significant portion of the collision system to fix not only this, but a number of other potential issues.
While I am under the hood of this, I will likely attempt to modify the hitboxes of the bogies, and remove them if at all possible to resolve some other collision problems, and the unsightly extra hitboxes.
This is more of a delay than an actual issue. With any luck it won't be an overly large delay at that.

Honestly I was looking forward to getting to work on linking tomorrow but oh well.

But the good news is that I was finally able to force a git push to update the repo, it even got to include the original dates!