Backlight abstraction and other changes (#439)

* redoes matrix pins, abstracts backlight code for B5,6,7

* slimming down keyboard stuff, backlight breathing implemented

* don't call backlight init when no pin

* cleans up user/kb/quantum calls, keyboard files

* fix pvc atomic

* replaces CHANNEL with correct var in breathing

* removes .hexs, updates readmes, updates template

* cleans-up clueboards, readmes to lowercase

* updates readme

keyboards/retro_refit/readme.md

@@ -0,0 +1,24 @@
+retro_refit keyboard firmware
+======================
+
+## Quantum MK Firmware
+
+For the full Quantum feature list, see [the parent readme.md](/readme.md).
+
+## Building
+
+Download or clone the whole firmware and navigate to the keyboards/retro_refit folder. Once your dev env is setup, you'll be able to type `make` to generate your .hex - you can then use the Teensy Loader to program your .hex file. 
+
+Depending on which keymap you would like to use, you will have to compile slightly differently.
+
+### Default
+To build with the default keymap, simply run `make`.
+
+### Other Keymaps
+Several version of keymap are available in advance but you are recommended to define your favorite layout yourself. To define your own keymap create file named `<name>.c` and see keymap document (you can find in top readme.md) and existent keymap files.
+
+To build the firmware binary hex file with a keymap just do `make` with `KEYMAP` option like:
+```
+$ make KEYMAP=[default|jack|<name>]
+```
+Keymaps follow the format **__\<name\>.c__** and are stored in the `keymaps` folder.