Write control registers

[jpenalbae]

A new cmd should be added in order to be able to write into control registers. Please note that control registers are local to each core/cpu, so a way to specify which cpuid control registers we want to overwrite should be implemented, and maybe a way to overwrite the control registers on every cpu at once.

This should also support logical operators so we don't have to deal with original values. For example if we want to enable write protect bit, we could just do a logical OR of cr0 register with 0x10000