Timeslider++

These are my fixes for @s1341's new timeslider (see #2040).

The first commit essentially introduces a new path calculator that computes a path from one revision to a new one (early version of that here: https://gist.github.com/marcelklehr/8208237), the rest of the changes are collateral to this: I stripped out partialTransition for example and reduced some other parts, too.

My second commit addresses #2065 as well as the OccupyChar issue. I hope it doesn't cause any bugs, accidentally.

Lastly, there are still a few soar spots in the timeslider codez that should be addresses (e.g. try going from rev#36 to rev#25, i think), so.. NOT READY yet.