[vault] porting the-vault version update logic

Ability to upgrade old repository/tree structure to support backups
done with previous the-vault/vault version

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
qRegisterMetaType results in unused variables

suppress compilation warning/error

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>