Keyboard: handwired/fivethirteen Refactor, Configurator support, and readme cleanup...

Keyboard: handwired/fivethirteen Refactor, Configurator support, and readme cleanup (#4559)

* handwired/fivethirteen: refactor

- Layout macro KEYMAP renamed to LAYOUT
- Default keymap
  - now uses #include QMK_KEYBOARD_H
  - Removed redundant KC_TRNS definition
  - Removed deprecated fn_actions and action_get_macro functions.

* handwired/fivethirteen: Configurator support

* handwired/fivethirteen: readme cleanup

Restructured readme file to be closer to current QMK template.

Couldn't find a photo of an assembled fivethirteen, so deleted the
reference to the photograph.

Renamed to readme.md