Make user search optional

Issue Summary

Greetings,

At the moment user module implements search interface and provides its tab on the search page which is imposible to disable. There is no way to remove core user search tab. Our proposition is to make it optional so administrator will be able to decide whether he needs this search or not.

Reason: It is very rare when simple user search (search by user name only) is need. We prefer nodeprofile.module to extend user profile, somebody prefers core profile. Anyway it is needed to develop specific user search module which will search by profile fields or use one of existing modules. It is easy to add a new search module but it is impossible to remove core user search.

Thank you.