Allow cycle by cycle execution

[facundoq]

Right now, the execution model works instruction by instruction.

Allow each instruction to generate a list of microcode instructions to perform cycle by cycle execution. In each cycle only one byte from memory can be loaded.

This execution model reflect both instruction loading and execution delays. For example a 5 byte instruction should take 5 cycles to load, 1 to execute, and if operands need to be saved in memory 1 or 2 extra cycles to do it.