Segment layering & effect blending improvements

- Photoshop-style segment/layer blending
- return of strip ABL
- remove global LED buffer in favour of segment-local buffer
- new effect blending modes/transitions
- custom palettes moved out of WS2812FX class
- increased limits (matrix size, LED RAM)
- added "rainbow"-mode colorwheel
- replaced palettes with gamma unmodified ones
- move gamma adjustment to last step before sending to LEDs
- Segment & WS2812FX class reorganisation (mutable members, reordered members, protected members)

usermods/Cronixie/Cronixie.cpp

@@ -247,7 +247,7 @@ class UsermodCronixie : public Usermod {
         
         if (backlight && _digitOut[i] <11)
         {
-          uint32_t col = gamma32(strip.getSegment(0).colors[1]);
+          uint32_t col = strip.getSegment(0).colors[1];
           for (uint16_t j=o; j< o+10; j++) {
             if (j != excl) strip.setPixelColor(j, col);
           }