Adds suppor for passing regular strings to db `put`/`get`/`delete`, to avoid having to hex-encode when operating on fixed-key items like `SnapshotSyncStatus`, `SnapshotRecovery`  etc.
Signed-off-by: Maxim Zhiburt <zhiburt@gmail.com>
Co-authored-by: Martin Holst Swende <martin@swende.se>