Save position messages in CSV

I added a menu option to extract (From, SNR, Time, Distance) data from position messages and save the data in a CSV file on the phone. Afterwards the file could be viewed/uploaded to cloud/analyzed by existing Android apps (I use Google Files, Drive and Sheets). My use case is for testing signal strength for my new nrf52 board and I do not have an easy access to RangeTestPlugin from nrf52. I think this may be a low-cost substitute for the plugin for other Android users as well. The PR is in Save messages in CSV file by vfurman-gh · Pull Request #260 · meshtastic/Meshtastic-Android · GitHub. LMK what you think.