SelfUpdateCommand: initial groundwork for --rollback
SelfUpdateCommand: only use 1 rollback snapshot at a time
SelfUpdateCommand: do not delete old snapshots, allow user to clean them
SelfUpdateCommand: removed unneeded return
Merge remote-tracking branch 'chr0n1x/feature-selfupdate-rollback'
Add version arg, docs for --rollback and reorganize the code, refs #2522