Adjusted parseNumber to not consume any of " \n'()"

parseNumber was consuming the ending parenthasis needed for the method
call code.
Added UnknownKeyword case for ScriptError
Added experimental new version of parseExpression

Supports the keyword "dim", comments, and empty lines.
Added "print" keyword support to new expression parser
Added support for assignments to parseExpression
Added commas and curly-brackets to acceptable after-number characters

The number parser didn't like "{ 0, -1 }" because of the comma after 0,
and it also didn't like "{0, 1}" because of the curly-bracket after 1.
Added parseAssignmentNoLeadingSpace

Going to use this so that the expression parser can consume extra spaces
instead.
Added custom version of createParserForwardedToRef that allows arguments

Need it for some testing, but I've created an issue on the FParsec issue
tracker suggesting it or something similar for the library.