main: memory operations now rely on a bus ID (set for CPUs and controllers).
main: CPU/controller init status is now checked prior to registration.
chip8: added CPU init status check during setup.
nes: added CPU & controllers init status check during setup.
main: updated documentation wrt video frontend parameters.
main: added CPU interrupt support.
nes: added initial support for RP2A03 CPU.
nes: added initial PPU support.
nes: clock rates are now derived from a master clock.