drawPixel and getPixel now inline, 3x faster

Thanks to Myndale for that suggestion
gb.sound.prescaler controls playback speed

value automatically adjusted when using gb.setFrameRate for playback
speed to be the same
SETTINGS_PAGE changed (breaks compatibily!)
changelog updated
bitmap encoder moved to a separate repo
bootloader updated to experimental v2 by Jonnection
hex files updated
useless constructor removed
readme slight improvement
utilities removed from main repo
changelog updated
License LGPL3 added
license added to readme
bug when NUM_CHANNEL is et to 0 fixed
few hex added
gb.display.getBuffer() added
changelog updated
pixel-wise collision detection added
displays voltage when out of battery
INVERT color added