Reduced the complexity of readMemory
Implement write-only bits in sound registers FF10-FF2F, including non-registers in that range.

References:
* Blargg's CGB audio tests, 01-registers #2 "NR10-NR51 and wave RAM write/read"..
* Blargg's CGB audio tests, 01-registers #3 "NR52 write/read".
Clear registers in I/O RAM when disabling the APU.

References:
* Blargg's CGB audio tests, 01-registers #5 "Powering APU off should write 0 to all regs".
Ignore writes to registers FF10-FF25 while the APU is off.

References:
* Blargg's CGB audio tests, 01-registers #6 "When off, should ignore writes to registers".
Merge pull request #6 from Nebuleon/correctness

Emulation correctness: Part 1, audio registers
Merge branch 'master' of https://github.com/Drienn/GameYob
Fixed garbage when gameboy screen is re-enabled
Wait for Vblank instead of Vcount to fix dsi-mode
Serial interrupt is triggered immediately for internal clock when nifi isn't on
Basic save states
States: sram saved properly, 10 slots, sound restored properly.
Attempt to make states more future-friendly
More accurate serial interrupt timing (when nifi is off...)
Wait for VBlank on by default to stop dsi-mode crashes
Replaced FPS output option with just Time output
Settings are saved
Restored readIO
Fixed dsi-mode check for vsync
dsi testing
Force interruptWaitMode to be set to one