General RGB matrix fixes (#2931)

* Added Modular keyboards L,R and NUM

Created code modules for the 3 modules of the modular keyboard.
Original idea by MechboardsUK. Uses i2c implementation similar to lets
split

* Remove modular from master

This is to fix incorrect branching

* General fixes for RGB_matrix

- Complited speed support for all effects
- Fixed raindrop effects to initialized after toggle
- Fixed raindrop effects to use all available LEDs
- Fixed effect step reverse function
- Moved RGB_MATRIX_SOLID_REACTIVE under correct flag

* Documentation update for RGBmatrix

* More doc updates

quantum/rgb_matrix.h

@@ -64,7 +64,6 @@ typedef union {
 
 enum rgb_matrix_effects {
 	RGB_MATRIX_SOLID_COLOR = 1,
-    RGB_MATRIX_SOLID_REACTIVE,
     RGB_MATRIX_ALPHAS_MODS,
     RGB_MATRIX_DUAL_BEACON,
     RGB_MATRIX_GRADIENT_UP_DOWN,
@@ -77,6 +76,7 @@ enum rgb_matrix_effects {
     RGB_MATRIX_RAINBOW_MOVING_CHEVRON,
     RGB_MATRIX_JELLYBEAN_RAINDROPS,
 #ifdef RGB_MATRIX_KEYPRESSES
+    RGB_MATRIX_SOLID_REACTIVE,
     RGB_MATRIX_SPLASH,
     RGB_MATRIX_MULTISPLASH,
     RGB_MATRIX_SOLID_SPLASH,