Refactored Bluetooth support to make adding new Bluetooth modules
easier in the future.
* Remove `OUT_BLE` key from QMK's keymap. `OUT_BT` is all we need now
as there's no difference anymore.
* Made BLUETOOTH_ENABLE build option legacy as not to break existing
keymaps (Falls back to existing EZ Key support if on)
* Removed `ADAFRUIT_BLE_ENABLE` build option
* Created new build option `BLUETOOTH` with module option (Currently
`AdafruitEZKey` & `AdafruitBLE`)
* Moved all LUFA bluetooth key/mouse events under `BLUETOOTH_ENABLE`
ifdef with selected modules output.
This implements some helper functions that allow sending key reports
to an SPI based Bluetooth Low Energy module, such as the Adafruit
Feather 32u4 Bluefruit LE.
There is some plumbing required in lufa.c to enable this; that
is in a follow-on commit.
