adds Xyverz's keymaps (#615)

adds Xyverz's keymaps (#615)

* Adding my own keymaps to the following keyboards:

Planck, Preonic, Atreus, Ergodox

* Delete dvorak.png

Not reflective of my layout.

* Delete readme.md

file cleanup, removing file that doesn't apply to my layout.

* Delete old_keymap.c

file cleanup

* Delete README.md

file clean up.

* Delete README.md

file cleanup

* Delete keymap.c

file cleanup

* Changed behavior of _DVORAK layout's KC_RSFT to SFT_T(KC_ENT) for flexibility's sake.
Updated the rest of the keymap to reflect the current (as of 19:37 on 08 Aug 2018) default
layout and default makefile.