Add support for Multipoint SiK radio modems in 3DR modem setup page

Hi,

I'd kindly ask you to add support for Multipoint SiK firmwares in 3DR modem setup tab, since for AntennaTracker it is really useful to use separated slave radio modem. I have great success with Multipoint modems, but modify params with AT commands is annoying.

Either add the Multipoint specific parameter labels too (S15-S18) or make them visible once Multipoint firmware is detected.

(Here is the description of Multipoint commands: https://github.com/RFDesign/SiK_Multipoint/blob/master/README.markdown)

Many thanks in advance, in bealf of all AntennaTracker users.
regards
Adrian

Start in the Mission Planner 3DR modem setup tab and read the linked SiK_Multipoint README for the S15-S18 parameter definitions. Done means Multipoint firmware users can see and modify the relevant parameters in the setup page, either through dedicated labels or conditional visibility.

Written by the indexing model from the issue text.