Use a gdbus-codegen-ed GDBusInterfaceSkeleton and GApplication

... instead of manually acquiring the bus, registering objects on it,
dealing with the details of handling methods and parameters,
unwrapping parameters from GVariant, dealing with timeouts, etc..

https://bugzilla.gnome.org/show_bug.cgi?id=731976
Remove unused MINER_OBJECT_PATH

https://bugzilla.gnome.org/show_bug.cgi?id=731976