rebase
Fixed facility arugment item type error, fixed getTrueVarExp not providing a math type, added copy ability to ProgramStringExp
insignificant changes to popul.
grabbing more information for programVariableEntries (a variable's corresponding facility, originating concept, etc).
added information needed for translation purposes to the symbol table
cleaned up some of the logic in my edits to populator and added some additional comments to what I have there so far -- I'll be starting a new branch for future changes (still learning how to properly use github/git workflow).