import UART transmitter from nexys4 gpio demo.
begin adding UART component.
Write letters to UART @ ~1Hz for debugging.
update simulation to use actual container instead of a parallel
implementation of container.
set outputs for uart debugging version of container.
fix uart TX timer calculation.
add extra source files to project.
add uart files to simulation command line
make compatible with ghdl simulation.
add activity LED to debug monitor.
add generation of bitstream for UART.
cleanup pllclock.  make note for simulation of uart monitor
interface (clock issue).
implement UART receiver.
connect reset button to uart monitor.
add banner message when uart monitor is reset.
improve character handling with type conversion wrappers.
fix bug with sounding bell when input buffer full.
fix embedded control characters in banner and help messages.
add one cycle delay after tx_ready rises before sending in
attempt to stop characters being dropped on TX.
fix inverted sense of reset line.
print ? for unknown characters for now.
implement ^R (redraw), ^U (erase line), backspace, delete and
enter editing controls.
Implement 'h'/'?' command to display monitor help.
Reduce command input buffer to 64 bytes.
move uart monitor from pixelclock to cpuclock, adjusting baudrate
calculators in the process.
implement various command parsing functions.
add hex output functions.