Add support for TMOD3 fixed position.

[nseidle]

There are times when I need to set the static position of the receiver CFG-TMODE3 so I added setStaticPosition.

This PR:

• Adds setStaticPosition that enables the setting via ECEF or Lat/Long coords
• Adds an example demoing the use

I think this is a good example of a function that should be converted to set/getVals. The ZED is pretty much the first receiver to support TMODE3 so we don't have to worry about <v27 protocol issues. The function would go from 50 lines to perhaps 8 and remove the need for read/modify/write steps (faster!).

[nseidle]

I think all changes are committed. Please have a look at your convenience.

[PaulZC]

Nice one - thank you! Please merge and delete branch at your convenience...