* introducing external MLink module telemetry as module PPM subtype
* implemented fix for sensor discovery display not showing all detected sensors (is in separate PR too)
implemented PPM subtypes in Companion
* add PPM subtype to model printer
finalize subtypes for PPM in Companion
* added logic to try to use HW UART with inverters turned off first (e.g. NV14), then, if not successfull use soft serial inverted (== uninverted data due to HW inverters on PCB)
changed start bit detection IRQ priority from 5 to the previous 0 (also in separate PR)
* extended telemetry timeout to 2s due to slow Mlink RSSI update rate
* changed the "NOTLM" sub-type texts to:
- "No Telem" for 128x64 (this is the max numbers of characters it can take)
- "No Telemetry" everything else including Companion
* Companion:
- lower case 1st charachter on PpmSubTypeStrings to ppmSubTypeStrings
- added telemetry hooks for ppmSubTypeStrings stringx
* simplified serial port initialization for MLink telemetry
* editorial change: corrected obsolete comment
