add zeroconf support based on qt4 libraries (#667)

* 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

* added bonjour/zeroconf service discovery to the json interface.

When clients are also modified, they can
- find hyperiond on the network much more quickly than ping/portscan;
- find multiple instances running on different ports instead of assuming 19444

* Moved zeroconf calls to hyperiond.cpp

* Added mDNS/zerconf/bonjour registration for proto server

Added config options.
        "jsonServer" :
        {
                "port" : 49444,
//              "mDNSDescr" : "hyperiond jsonServer blah de blah",
                "mDNSService" : "_hyperiond_json._tcp"
        },

* cleaned up a couple of compiler warnings

* 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

* moving to my fork of rpi_281x

* Now uses the led device name and hostname to create the annouce name


Former-commit-id: abfa51bcf359cafa63338181c1b83ecfd231bc87

CMakeLists.txt

@@ -15,6 +15,7 @@ SET ( DEFAULT_X11        OFF )
 SET ( DEFAULT_SPIDEV     OFF )
 SET ( DEFAULT_WS2812BPWM OFF )
 SET ( DEFAULT_WS281XPWM  OFF )
+SET ( DEFAULT_ZEROCONF   OFF )
 
 if (APPLE)
 	SET ( DEFAULT_OSX ON )
@@ -39,6 +40,9 @@ else ()
 endif ()
 
 # set the build options
+option(ENABLE_ZEROCONF "Enable the avahi/zeroconf announce" ${DEFAULT_ZEROCONF} )
+message(STATUS "ENABLE_ZEROCONF = " ${ENABLE_ZEROCONF})
+
 option(ENABLE_AMLOGIC "Enable the AMLOGIC video grabber" ${DEFAULT_AMLOGIC} )
 message(STATUS "ENABLE_AMLOGIC = " ${ENABLE_AMLOGIC})