Removed the functional change I made for #874.
Introduced the term Radio Backup File to describe the eprom files that are uploaded from the radio.
The terms Radio, Tx and TX were used intermittently. I changed them all to Radio (naturally not in contexts having anything with the actual radio transmitting circuit).
Merge pull request #927 from opentx/dvogonen/introduce_backup_radio_concept_924

The term Backup Radio File introduced