MODE-1707, MODE-1610 - Implemented the JDBC metdata connector which also exposes imported foreign keys information

Part of the code was ported & adapted from 2.x, part was implemented from scratch. This PR contains both the functionality for MODE-1707 (connector implementation) and MODE-1610 (adding foreign keys information).

Together with this, the various DB profiles from 2.x have been ported & updated so it's possible to test against various database types.