Replace layer_stack with layer_switch

Merge branch 'layer_stack'

Fix switch_default_layer command

Add poker keymap with layer stacking

Add layer_stack files taking apart from action.c

Fix Make dependency file names

Change: 0 means default_layer in current_layer now

- current_layer indicates active layer at the time
- default_layer indicates base layer
- default_layer is used when current_layer is 0
- with this LAYER_BIT action works as overlay even if
  default_layer varies other than layer 0.

Add poker keymap with layer stacking.

Add layer stack

Merge branch 'actionfix'

Change struct key_t

Change action API

Merge branch 'transparent'

Add 'poker' target to Makefile.pjrc of gh60

Change keymap API

Make Transparent feature available to new keymaps.

Fix 'chage default layer' command.

Change ACTION_LAYER_SET_LAYER behaviour

Add transparent layer feature in gh60

Now includes LUFA-120730 in repository