Cleanup on ExpressionParser.  Flagged a definite error.  Added some additional log lines in exception blocks.
Replace some usages of AbstractList with List and Vector with ArrayList.  Fixed some duplicate add/removals of cells to the worksheet related to Mulblanks and Formulas. Added some additional debug log lines to show what's going on with the cell add/removes. Tidied up Mulblank.removeCell() to check for different invalid states and error conditions.