Merge branch 'master' into wffchecker-buttonpanel

* master:
  Added TruthTableColumn.java
Error handling works! Using exceptions, proper error messages, etc
Renamed grammar file, fixed TestButton exception possibility
More minor updates
added highlighting of errors
More minor fixes
fixed some highlighting errors
Added other characters per Eddie's request
Merged Kekai's highlighter thing

* 'wffchecker-buttonpanel' of ssh://github.com/PeterDrake/Logic:
  added highlighting of errors
merging wffChecker-buttonPanel into master