Migrate from flatfiles to PostreSQL

According distro splitting, it's time to migrate to PostreSQL. Flatfile database is ok, but the project raised and now we need to think about scaling. PostreSQL tables will provide much more efficient tools to store binary data (that is important regarding the blockchain caching) and additional types for storing, e.g. JSON or whatever.

Also SQL files for embedded/sample tables restoring (like current flatfiles) should be added.

The Pheix::Model::Database::Filechain will still present but will be marked as deprecated.

Tests should be updated/extended.