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/utils/CMakeLists.txt

@@ -1,4 +1,3 @@
-
 # Define the current source locations
 SET(CURRENT_HEADER_DIR ${CMAKE_SOURCE_DIR}/include/utils)
 SET(CURRENT_SOURCE_DIR ${CMAKE_SOURCE_DIR}/libsrc/utils)
@@ -12,6 +11,8 @@ add_library(hyperion-utils
 	${CURRENT_SOURCE_DIR}/ColorRgb.cpp
 	${CURRENT_HEADER_DIR}/ColorRgba.h
 	${CURRENT_SOURCE_DIR}/ColorRgba.cpp
+	${CURRENT_HEADER_DIR}/ColorRgbw.h
+	${CURRENT_SOURCE_DIR}/ColorRgbw.cpp
 	${CURRENT_HEADER_DIR}/Image.h
 	${CURRENT_HEADER_DIR}/Sleep.h
 
@@ -32,6 +33,9 @@ add_library(hyperion-utils
 	${CURRENT_HEADER_DIR}/RgbChannelAdjustment.h
 	${CURRENT_SOURCE_DIR}/RgbChannelAdjustment.cpp
 
+	${CURRENT_HEADER_DIR}/RgbToRgbw.h
+	${CURRENT_SOURCE_DIR}/RgbToRgbw.cpp
+
 	${CURRENT_HEADER_DIR}/jsonschema/JsonFactory.h
 	${CURRENT_HEADER_DIR}/jsonschema/JsonSchemaChecker.h
 	${CURRENT_SOURCE_DIR}/jsonschema/JsonSchemaChecker.cpp