As an alpha-user I want to keep my deprecated savings

[knoffi]

Migrator handles outdated json savings in DB:

• transforms outdated tavern savings
• transforms outdated impression savings
• transforms outdated offer savings

into updated object format.

• DataBase and Valiator use Migrator to load updated version of outdated data

Optional:

• Migrator behavior is controlled by a single list of object examples (resembling outdated data format)
• If migrator can not handle a format, then he sends unknown format to me (jsonbin.io or something else)