green caves: fix aiming
green caves: improve click event handling
green caves: fix mouse clicks when scrolled apparently
Started another try at the worst-case manual orderer.
worst case manual order building work
worst case manual order building work
Started separating the history tree from green caves (broke compile)
Continued separating the history tree from green caves
Continued separating the history tree from green caves
Continued history tree improvements. Compile works again.

The new history tree updates incrementally, so it's easier to
   understand.
There are still some graphical bugs and bugs where
   new branches are created when they shouldn't be.