added new project for basic switch reading

Made a couple of changes in a button_ISR_LED header file.  The file name
changed but the inclusion guards didn't, and I wanted to keep them
consistent with the file name.

Added the beginnings of a demo for pmod switch reading.
corrected button reader delay code

I had some errors in the C++_button_ISR_LED project that introduced gaps
in button port reading and doubled-up button port reading.

The two big things were that I left the call to the delay timer in
main's while(1) loop, and my soft countdown timers in the button handler
were not static, so they reset on every function call.
simplified switch reading

I am not dealing with finicky buttons like the button_ISR_LED project
was, and I am not turning ISRs on and off in response.  All I need to do
is read the current state and turn an LED on or off for each switch, so
all that stuff can happen in main.

Also renamed the "ISR_handlers" source file in the button_ISR_LED
project to "my_ISR_handlers".
removed a call to the delay timer

The delay timer doesn't exist anymore, but somehow I missed that on my
last build.  The pmod switch reading project wasn't set as the main
project, but somehow the first build attempt worked.  Oh well.  It's
cleaned up now.