ruleng: implement rule->action for simple rules

CMakeLists.txt

cmake/modules/FindJSON-C.cmake

src/main.c

src/ruleng.c

src/ruleng.h

src/ruleng_bus.h

src/ruleng_list.h

src/ruleng_model.c

src/ruleng_model.h

src/ruleng_ubus.c

src/utils.h

test/model.json

test/rules