Interrupt routine now running at 62Hrz rather than 2KHrz

The INT now refreshes the full screen on each call, which turns out is
much more efficient. I made this change to get ready to switch to using
the WDR rather than ints, and WDR max rate is 62hrz.
Moved frame update into the interrupt routine

This is very nice, it gets rid of a lot of code and signaling between
the interrupt code and the main thread. We are down to almost nothing
left in the main thread, just need to move the diagnostic screen into
the interrupt handler...