Adding a tab for the types

[samdus]

Our research group has an extensive use of domains and types. Therefore we would love to have a tab that describes them. This PR proposes a way to do this, along with an implementation for PostgreSQL. We will provide queries for other dbms over the summer.

Here's a preview of how the different PostgreSQL types are printed (Type of types are dynamics since each dbms has its own definitions):

[npetzall]

Would this be solving #487?

[samdus]

Yes, but only for PostgreSQL for now. We would need to develop the queries for other DBMS.

[VietThan]

@samdus @npetzall not sure if this is proper etiquette but I'm interested in this feature being merged in.

[npetzall]

@VietThan add a thumbs up to the description and we'll know that more people are interested in it.

I've finished up another about giving the ability to use AsciiDoc so I'm looking at multi arch for Docker and after that I'll have a look at this.

Just need to make sure that it's generic enough so that other Dbms than Pgsql can use it without becoming too strange.

[npetzall]

So mysql doesn't have UDT. MSSQL have both CRL and Table variants for it. Need to test them. But I think they both will fit. Still need to look a bit at Oracle and Informix. But since I'm no DB in any DB I'm mostly guessing.