Pull DB info helpers into state/backups.
Drop DBConnInfo.Validate.
Pull NewBackupsMetadata into state/backups.
Drop state.NewBackups.
DBInfo -> *DBInfo.
Paths -> *Paths.
Factor out getting the paths into a function.
Clarify a TODO comment.
Fold getPaths back into NewAPI.
Move machineID onto API.
Move machineID back inside Create.
Re-order an if statement.
Merge pull request #1174 from ericsnowcurrently/backups-cleanup

Minor backups cleanups.

These are changes that should have been in earlier patches.

(Review request: http://reviews.vapour.ws/r/485/)