Remove SQL scripts generation

We don't change JDBC scripts too often and even if we do that, it's not
so hard to copy/paste the script throughout all the supported platforms
instead of rely on the pretty old VPP tool and suffer from performance
degradation during regular day-to-day development.
Plus there is some bug in the VPP when it generates a script for the
Derby, so we end up with erroneous braces in the sentence:
```
MESSAGE_SEQUENCE BIGINT NOT NULL GENERATED ALWAYS AS IDENTITY (START WITH 1, INCREMENT BY 1),
```
I have to remove them manually each time I switch between Gradle versions

Author: artembilan