Prevent usage of Noble.Settings.setup if no keys are provided

[simjnd]

Further work on #24

This PR makes the engine bonk if Noble.Settings.setup is called without any arguments, or with {}.

Being able to detect a dictionary being empty actually took adding a new function in Utilities (not sure about the name, but at least it is explicit). I filed a bug report so that we can hopefully get rid of it and rely on the SDK-provided table.getsize.

Let me know what you think!