Feature set coordinates in the launch file

[amastrobera]

Allows the launch file to make the node communicate to the MT device its coordinates (in order to calculate the true north). It's a small convenience change using the existing API.

[amastrobera]

@efernandez FYI this needs to be merged with the #87 . I can do it myself once the previous lands

[fcolas]

Thanks again for this contribution. But same comments as #87