Rename to 'universum-extra' or 'universum-extended'?

[chshersh]

Well, personally, I just don't really like package-level Util. But serokell-util appeared earlier than universum and tried to solved some problems that universum solves. Since we now have universum, we can change goal of serokell-util:

1. Move something from serokell-util to universum.
2. Rename serokell-util so that name of the package shows this package goal.

Discuss?