* Keymap architecture
** Keymap definition modules are in src/Keymaps
** Each keymap has its own keymap setup routine
*** void setup_mapname_keymap(void) - keymap setup function
**** register a keycode map for each modifier combination
***** The keycode maps are in flash (ROM)
**** set up virtual devices for the keymap
***** virtual device to physical device mapping
***** associated virtual device function on activate/deactivate
***** initial state
**** set up function hooks used by keymap

** Keymap definition API
*** mapping keys
    #include "asdf_keymaps.h" 
**** asdf_keymaps_add_map() - called from 
     Assigns a specified keymap matrix (ptr to FLASH) to a given keymap and modifier type.
*** adding virtual devices - called from keymap setup routine
**** asdf_virtual_init()
***** Clears the virtual device table for the keymap
***** initialize first entry in virtual device table to NULL
**** asdf_virtual_add_device()
***** Accept a virtual device code, a physical device code, a default function, and a default initial value, and create a new entry in the virtual device table.
***** increment the virtual device table pointer and set next (last) entry to NULL


* DIP SWITCHES
  Note that the DIP switches are keys in the key matrix, which is initialized to
  the all unpressed state at startup. Since the keymap is initialized to 0, the
  keymap is consistent with the presumed initial state of the DIP switches. If
  the DIP switches are not set to Keymap 0, then their position will be detected
  as keypresses, and the correct keymap will be set.