* YMDK NP21: matrix and keymap refactor
- refactored layout macros
- LAYOUT_ortho_6x4 orients the keyboard with the USB port to the back instead of to the right
- LAYOUT uses the previous sideways orientation (included for backwards compatibility)
- removed redundant includes from ymdk_np21.h
- added a readme for the default keymap
* add Configurator layout support
