Make error messages for duplicate unique user/group/password/template names more user-friendly

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What steps will reproduce the problem?
1. Add a new User/Group/Password/Template with a name that has been added 
before, or update an existing one to which another has already been named.  
You'll get an ambiguous 500 error.

What is the expected output? What do you see instead?
1. Check to see if the name is taken and produce a more user-friendly and 
informative error message to the user rather than blindly trying to save it.

Original issue reported on code.google.com by joshdrum...@gmail.com on 5 Dec 2010 at 8:01

[GoogleCodeExporter]

Original comment by joshdrum...@gmail.com on 6 Dec 2010 at 1:26

• Changed state: Fixed

[GoogleCodeExporter]

Original comment by joshdrum...@gmail.com on 27 Dec 2010 at 8:11

• Added labels: Milestone-Release1.0, Usability