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

libsrc/jsonserver/JsonServer.cpp

@@ -29,6 +29,7 @@ JsonServer::JsonServer(Hyperion *hyperion, uint16_t port) :
 
 	// make sure the resources are loaded (they may be left out after static linking
 	Q_INIT_RESOURCE(JsonSchemas);
+
 }
 
 JsonServer::~JsonServer()