Add new build options to adb_usb

Fix ADB protocol issue #14

Fix comment of ADB signaling.

Add coding style and config.h options

Merge branch 'virtual_dipsw'

Fix bootmagic and eeconfig for virtual DIP SW

Add doc/build.md and doc/other_projects.md

Fix keymap for new actions

Merge branch 'action_refine'

Fix keymap of hhkb for new actions

Fix doc/keymap.md for new actions

Fix keymap of gh60

Fix ACT_MODS action and switch_default_layer command

Add file action_code.h

Fix doc/keymap.md

Fix ACTION_LAYER macros

Rename file layer_switch to action_layer

Refine ACT_LAYER and ACT_LAYER_TAP

- Remove ACT_LAYER_BITOP

Remove ACT_KEYMAP and ACT_OVERLAY

- Remove ACT_OVERLAY
- Rename ACT_KEYMAP to ACT_LAYER
- Add ACT_LAYER_BITOP

Fix BOOTLOADER_SIZE setting