* Keymap architecture
** Keymap definition module
   The keymap definition module defines:
*** The key mappings used by a keymap
*** The virtual devices required by the keymap
    This includes definitions for LED's and I/O lines, including their initial
    states, and default I/O operations such as toggle, pulse, etc.
*** Function hooks used by the keymap.
    Specifies which functions are used for operations such as key scanning, I/O,
    special keybindings, etc.

  Any special functions or logic required by the keymap are also defined and used in the module.

** 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

* Eliminate keymaps table and instead have table of keymap init routines with MAX_KEYMAPS entries
* keymap setup routine adds maps for each modifier to the keymap, now only rxcxMODIFIERS instead of rxcxmodifiersxkeymaps
* remove the keymap index from the add_map() call.
* select_keymap() will call setup routine for the g
iven keymap.
* Each keymap sets its own num_rows and num_columns, per matrix for each modifier

* 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.