Keyboard: Add support for the KBD4x (#4036)

* Generate a new project for the KBD4x

* Specify the possible layouts for the KBD4x - MIT and grid

* Fill out the readme for the KBD4x

* Configure the default keymap and wiring configuration as specified on http://qmkeyboard.cn/

* Add info.json for QMK Configurator

* Enable backlight support for the KBD4x

* Standardise on LAYOUT_planck_mit/LAYOUT_ortho_4x12 layout names

* Add whitespace so the Readme will render correctly

* Disable mouse keys support for the KBD4x to make the firmware small enough

keyboards/kbd4x/keymaps/default/config.h

@@ -0,0 +1,19 @@
+/* Copyright 2018 sevenseacat
+ *
+ * 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/>.
+ */
+
+#pragma once
+
+// place overrides here