Change observer following to use locked_to methods

Created by: dylanstrategie

• Change Follow into Haunt, because flavor
• Add Stop Haunting verb (stop following), if you can't figure out how it works
• Following mobs now lock you to them, instead of the extremely convoluted method used before. This will make ghost following a ton more responsive, stop the massive wall of delayed movement observers, and possibly even reduce lag (one can hope) given a while loop was removed
• You can still move while locked to mobs. Doing so will have you stop following them, as it was handled before

This was tested and works properly on monkeys and singularities (although monkeys being switched doesn't seem to update your position). Since targets are limited to mobs, the nuclear disk and the singularity, this also shouldn't cause problems with any object that uses locked_to like vehicles