Implement DeviceGenerator qtc plugin

src/qtcreator/CMakeLists.txt

src/qtcreator/devicegeneratorplugin/CMakeLists.txt

...eator/devicegeneratorplugin/DeviceGeneratorPlugin.json.in

...qtcreator/devicegeneratorplugin/devicegeneratorplugin.cpp

src/qtcreator/devicegeneratorplugin/devicegeneratorplugin.h

...ator/devicegeneratorplugin/devicegeneratorplugin_global.h

...or/devicegeneratorplugin/devicegeneratorpluginconstants.h