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

libsrc/leddevice/LedDeviceFactory.cpp

@@ -363,8 +363,11 @@ LedDevice * LedDeviceFactory::construct(const Json::Value & deviceConfig)
 		const int dmanum = deviceConfig.get("dmanum", 5).asInt();
                 const int pwmchannel = deviceConfig.get("pwmchannel", 0).asInt();
 		const int invert = deviceConfig.get("invert", 0).asInt();
+		const int rgbw = deviceConfig.get("rgbw", 0).asInt();
+		const std::string& whiteAlgorithm = deviceConfig.get("white_algorithm","").asString();
 
-		LedDeviceWS281x * ledDeviceWS281x = new LedDeviceWS281x(gpio, leds, freq, dmanum, pwmchannel, invert);
+		LedDeviceWS281x * ledDeviceWS281x = new LedDeviceWS281x(gpio, leds, freq, dmanum, pwmchannel, invert, 
+			rgbw, whiteAlgorithm);
 		device = ledDeviceWS281x;
 	}
 #endif