Added 'LD DE, nn'
Added 'LD (DE), A'
Added 'INC DE'
Added 'INC D'
Added 'DEC D'
Added 'LD D, n'
'RLX' and 'RRX' instructions shouldn't alter flag Z
Added 'RLA'
Refactored registers as classes
Added 'JR n'
Added 'LD A, (DE)'
Added 'DEC BC'
Added 'INC E'
Added 'DEC E'
Added 'LD E, n'
Added 'RRA'