Lets split eh (#3120)

* Line ending stuff again

* Added Let's Split Eh? Files and updated #USE_IC2 checks to also include th EH revision (can only be used in I2C)

* Added personal keymap, updated some of the EH files

* Created new keyboard file for testing "lets_split_eh" will merge into lets_split once fully functional

* Added split code from lets_split, removed pro micro imports and LED code

THIS IS WORKING CODE, WITHOUT RGB AND BACKLIGHT

* Took back original Lets Slit files for the lets_split keyboard, working in the lets_split_eh folder for now

* Updated eh.c

* More rework of the I2C code, added global flags for split boards.

* Introduced RGB over I2C, having weird edge case issues at the moment though

* Fixed weird I2C edgecase with RGB, although still would like to track down route cause..

* Changed RGB keycodes (static ones) to activate on key-up instead of key-down to elimate weird ghosting issue over I2C

* Lots of changes, mainly externalized the Split keyboard code and added logic for only including when needed.

- Added makefile option "SPLIT_KEYBOARD" that when = yes will include the split keyboard files and custom matrix
- Split keyboard files placed into quantum/split_common/
- Added define option for config files "SPLIT_HAND_PIN" FOr using high/low pin to determine handedness, low = right hand, high = left hand
- Cleaned up split logic for RGB and Backlight so it is only exectuted / included when needed

* Updated documentation for the new makefile options and #defines specific to split keyboards

* Added a bit more info to docs, so people aren't confused

* Modifed Let's Split to use externalized code, also added left and right hand eeprom files to the split_common folder

* Removed some debugging from eh.c

* Small changes to keyboard configs. Also added a default keymap (just a copy of my that_canadian keymap).

* Added a README file to the Let's Split Eh?

* Changed it so RGB static updates are done on key-up ONLY for split boards rather than all boards. Also fixed leftover un-used variable in rgblight.c

* Updated default keymap and my keymap for Let's Split Eh? Updated the comments so it reflects RGB control, and removed audio functions.

* Fixed lets_split_eh not having a default version

* Removed "eh" references from lets_split folder for now

* Took lets_split folder from master to fix travis build errors, weird my local was overriding.

* Changed LAYOUT_ortho_4x12_kc -> LAYOUT_kc_ortho_4x12 to match bakingpy and others

* Removed rules.mk from my lets_split keymap, not needed

* Updated the config_options doc to better explain the usage of "#define SPLIT_HAND_PIN"

quantum/keymap_common.c

@@ -29,6 +29,10 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include "backlight.h"
 #include "quantum.h"
 
+#ifdef SPLIT_KEYBOARD
+    #include "split_flags.h"
+#endif
+
 #ifdef MIDI_ENABLE
 	#include "process_midi.h"
 #endif
@@ -134,21 +138,39 @@ action_t action_for_key(uint8_t layer, keypos_t key)
     #ifdef BACKLIGHT_ENABLE
         case BL_ON:
             action.code = ACTION_BACKLIGHT_ON();
+            #ifdef SPLIT_KEYBOARD
+                BACKLIT_DIRTY = true;
+            #endif
             break;
         case BL_OFF:
             action.code = ACTION_BACKLIGHT_OFF();
+            #ifdef SPLIT_KEYBOARD
+                BACKLIT_DIRTY = true;
+            #endif
             break;
         case BL_DEC:
             action.code = ACTION_BACKLIGHT_DECREASE();
+            #ifdef SPLIT_KEYBOARD
+                BACKLIT_DIRTY = true;
+            #endif
             break;
         case BL_INC:
             action.code = ACTION_BACKLIGHT_INCREASE();
+            #ifdef SPLIT_KEYBOARD
+                BACKLIT_DIRTY = true;
+            #endif
             break;
         case BL_TOGG:
             action.code = ACTION_BACKLIGHT_TOGGLE();
+            #ifdef SPLIT_KEYBOARD
+                BACKLIT_DIRTY = true;
+            #endif
             break;
         case BL_STEP:
             action.code = ACTION_BACKLIGHT_STEP();
+            #ifdef SPLIT_KEYBOARD
+                BACKLIT_DIRTY = true;
+            #endif
             break;
     #endif
     #ifdef SWAP_HANDS_ENABLE