re-implement setting reward address

[0pcom]

since we are moving displaynodeip to the visor's conf struct, it is necesary to have that settable via config gen, and to change the config priv subcommand so that it produces the file with the new format

the json forrmat of the reward address file was dropped, and the filename changed to reward.txt

the format of this file can now be easily reproduced by any user, without needing to use the cli command

the existing privacyconfig implementation was either removed or commented out

This PR needs erson's PR for changes to the visor's config struct