implemented let translate for single and multiple assignments

sub-string assignments are not yet implemented
modified getOperand() to support getting references when selected
modified new translate() to handle expression mode calls correctly
changed findCode() to mark open parentheses tokens unused for errors
updated variableErrStatus() to handle number and any data types

made many translator functions public for command translate routines
added drop() function to DoneStack class
added assign list codes as associated codes for assign codes
added TokenStack class for holding token pointers
  (which are automatically deleted when stack goes out of scope)