[GPIO] Fix 3 minor GPIO issues

• Events were triggered on startup.  Previously the state was set to 0,
  and events would then only be raised when changed.  Since the variable
  used in the NC check was removed, I now use the debounce code to
  prevent startup events by setting the time for initialized events on
  startup.

• PiFace table is part of the same table on the GPIO UI page and needed
  to be cleaned up from when I added wiringPi numbers to the built-in
  GPIO table.

• Put rising and falling event drop-downs on separate lines so the page
  is rendered more cleanly if users have really long event names.