Add sk6812rgbw support (#666)

* Removed -HUP so the default -TERM signal is sent instead.
- hyperiond only listens for TERM and INT. HUP is often used to get an exe to reread its config

Changed pgrep to add '-x' so it wont partial match on the exe name.
- I have multiple instances with multiple hyperiond-instance1 names
- this ensures the service script only kills the right process

* reversing errant change to hyperion.systemd.sh

* adding support for SK6812 - not working yet

* Changed rpi_ws281x submodule to be penfold42's fork

* Set White to zero for now

* starting on the code to make the White led do stuff

* Added some basic whie led calculation
white = min(r,g,b)
r-=w, g-=w, b-=w

* cleaned up a couple of compiler warnings

* updated strip type to use corrected RGBW strip type
(the SK6812RGBW datasheet is wrong)

* moved bitpair_to_byte initialiser to (hopefully) work with older GCC

* compiler warning in udp driver
removed some tabs in ws2812b.cpp

* formatting - spaces to tabs

* moved rpi_281x to tag sk6812-v1.0

* attempt #3 at migrating the rpi_281x submodule to my fork/branch

* moving to my fork of rpi_281x

* Started implementing multiple RGB to RGBW conversion options

a quick hack has been implemented inside WS281x.cpp but ive started
moving this to RgbToRgbw.cpp for reuse by other led device types

* migrated RGB to RGBW conversion to RgbToRgbw.cpp


Former-commit-id: ff8e9038c4bb8203b71b42d12bf23be4abcc0b3b

include/leddevice/LedDevice.h

@@ -5,6 +5,8 @@
 
 // Utility includes
 #include <utils/ColorRgb.h>
+#include <utils/ColorRgbw.h>
+#include <utils/RgbToRgbw.h>
 
 ///
 /// Interface (pure virtual base class) for LedDevices.