Meira Refactor (#14566)

* clean up keyboard header files

* use #pragma once include guard
* convert tabs to spaces
* remove redundant #include statements
* update revision references to main header (`../meira.h` -> `meira.h`)

* refactor default keymap

* use LAYOUT as layout macro reference
* use enum statement for layer indexes; make layers contiguous
* use four-space indent
* update keycode grid alignment

* update layout macro aliases

* move layout macro aliases to info.json
  * alias KEYMAP to LAYOUT_ortho_4x12 so the user keymaps don't have to be edited

* touch up meira.h

There's no Planck MIT layout reference here.

* add copyright headers

* workaround patch for grahampheath keymap

The `matrix_init_kb()` function in `meira.c` calls `backlight_set()`, but the grahampheath keymap disables Backlight to make space for Audio, causing the firmware to fail to compile.

This commit wraps the `backlight_set()` call in an ifdef statement, so the call is excluded if Backlight is disabled.

* clean up rules.mk inline comments

* re-order rules.mk settings

* clean up readme.md

* correct link to keyboard image
* change metadata section to unordered list
* spelling corrections
* update make instructions and Docs links

keyboards/meira/featherble/featherble.c

@@ -1 +1,17 @@
+/* Copyright 2017 Cole Markham, WoodKeys.click
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
 #include "meira.h"