Added logging using F_OPLogger wherever there were traces.
Errors will be added to an array if the optimizer finds invalid operations involving constants (e.g. (inv 0))
Handles: * size vars in fixed size mode, * unary operators with constant argument, * binary operators with constant arguments. Doesn't handle as of yet: * constant inputs, * folding chained, compatible binary operators, e.g. (X-2)+(3-Y)