It was not properly including the "config_common" files, and was causing it to break on the configurator.
Additionally, updated this to use the split common code.
* Remove chording as it is not documented, not used, and needs work.
* Make Leader Key an optional feature.
* Switch from `PREVENT_STUCK_MODIFIERS` to `STRICT_LAYER_RELEASE`
* Remove `#define PREVENT_STUCK_MODIFIERS` from keymaps.
