Remove additions to the interface

[simendsjo]

I see you merged my (incomplete) cleanup branch. There's a couple of methods that I only used for testing in that branch located at the top of the file. It's not very well thought out, so I recommend that you remove the methods before pushing to the package repository.

[Abscissa]

Which ones?

[simendsjo]

createCommand, queryEager, queryLazy, exec and FiberConnectionPool. I think a connectionpool exists elsewhere.