Split unique unit behaviors into separate scripts.

Execution order matters: The scripts for unit behaviors have to load
before the generic script in order to run properly.  Also removed a
clause that caused units to stop moving forever if they ever reached a
full-stop. Also moved utilities to LibRevel. Again. But it should
probably actually work this time! There were a lot of conflicts and
issues due to removed states in the State enum making prefabs default to
invalid values. Any regressions should be reported.