The decoder needs a serious refactoring/decoupling.
The UI just dumps bits of the received packets into a console window, whcih scrolls too quickly in an AIS-dense area with a good antenna.
Turns out 0x10088000 - 0x10089fff is not the right place. It's 0x40041000, and is only 256 bytes!
Move PPM to correct place, change representation to PPB for finer control.
Reset PPB value to initial value if read value out of bounds.
Clip PPB value on write to permitted bounds.
Contributes to resolution of issue #11.
