Improvement: Make it possible to initialize KVS when snapshot with ID=0 is not available

[arkjedrz]

Right now if snapshot with ID=0 is not available then KVS is not able to initialize.
Ideas:

• Add parameter to builder with snapshot ID - with 0 as default.
• Make automatic loop that tries to load until succesful and return loaded snapshot ID.
  • This might not be preferred, as this performs implicit and surprising operation underneath.