More Z80 instruction params tested.
Finished rough testing of all instruction parameters

Also, removed the need for the memory flag bit, simplifying parameter testing
Various improvements to opcode building

* Modified Z80 parameters to be Longs and not Doubles so that the Assembler will handle the details of rounding down expressions &c and the opcode-builder doesn't have to worry
* Added tracking of which parameter has the IX/IY value and which param has the main value, this will be needed for outputting the opcode & data
* IX/IY prefix bytes are outputted