Rework DB layer for better performance and enable indexes

[Frostman]

• bolt schema improvements
• • bucket per type
• • simplified keys w/o namepaces and kind in it, for policy objects key will return ns/name
• • use binary.LittleEndian.PutUint64 for version encoding
• • replace current key with "reference" that include kind, namespace and name
• • deleted flag should be handled outside of DB layer, it's just a Versioned object with deleted field
• • do setting of new generation inside same transaction
• add indexes support
• • implement indexes primarily w/o using reflection
• • support list / first / last indexes
• • automatic index for versioned object to query last version
• • get should use index for getting last version of the versioned object
• cover all parts of new DB layer with at least basic unit and integration tests
• encoding improvement
• • separated codec w/o kind manipulation for higher performance
• • use god or message pack by default
• • codec benchmark to find best codec for DB