Delete File by path admin message

[garthvh]

Years later there remains no way to delete the CSV file for range tests, create an admin messages so this file can be deleted.

[geeksville]

This issue has been mentioned on Meshtastic. There might be relevant details there:

https://meshtastic.discourse.group/t/how-to-reset-the-csv-file/9430/5

[andrekir]

this still works:

powershell: Invoke-RestMethod -UseBasicParsing -Uri "http://meshtastic.local/json/fs/delete/static?delete=static/rangetest.csv" -Method Delete

maybe one of the web devs can implement this on the web client.

[thebentern]

We can probably re-use that underlying method. Adding an admin message will let us do it on non-wifi hardware like Pico and Nrf52.