-) Scoping functions are not handled generally
-) Added evaluate_for_subcategories function
-) Added debug_cart and debug_products and debug_values variables

Signed-off-by: Reinhold Kainhofer <reinhold@kainhofer.com>

Version 4.0: Fix globals warning; Add Values_Debug variable; Add contains_any/contains_all functions

Special care is taken (using a global array of messages...) to ensure that the message is not printed twice...

The shunting yard algorithm had to be severely extended (by using a temporary operand stack for the function arguments, and by storing the type of the previous token to distinguish unary operators from binary)

Version 2.3.0: Add NoShipping to not offer any shipping at all; fix shipping costs when Shipping= is omitted

Version 2.2: Add length unit conversions; add tilde operator to check variable start; Fix chained comparisons

Implement arithmetic operations, create advanced version