calling lua from dbus
It is possible to send a lua command to darktable via its DBus interface. The method
org.darktable.service.Remote.Lua takes a single string parameter which is interpreted as a lua command. The command will be executed in the current lua context and should return either nil or a string. The result will be passed back as the result of the DBus method.
If the Lua call results in an error, the DBus method call will return an error
org.darktable.Error.LuaError with the lua error message as the message attached to the DBus error.