Add missing line in PicSim.UI.csproj.
Finish IORegisterViewModel.
Start implementing UI for PORTA, PORTB.
Finish RS232 COM port.
Fix some aspects of interrupt handling.
Correct handling of data latches and external input for PORTA & PORTB.
Fix property change notifications for CommPortInfo.
Implement RB0INTInterruptContributor.
RS232: Detect whether hardware is connected or not.