Made TreePanel display error strings when nodes containing errors are
under the mouse. Fixed CaseTentOrGrass to take into account the fact
that case rules are now stored at transitions. Commented out a check for
"status == -1" in BoardState.getStatus(), causing the recomputing of
formerly cached values. Some glitch exists with recoloring: for
CaseTentOrGrass, if 2 branches are made, and the rule is not applied
correctly, the second branch does not properly update color.