Mixed case usernames can be created in the setup wizard

A report from a user:

> I downloaded and installed an eval of Jira last night - great product
> BTW - I used it in my previous job.
>
> I have resolved my own issue, but thought you might be interested to
> hear about the problem, in case it is a bug you want to fix.
>
> During the setup process I created an admin user account - it allowed me
> to use mixed case for the user id so I picked PaulHomes - a familiar
> userid for me. Later I added a second account - but the Add User page
> required all lowercase so I picked iansutton. I continued to login
> using PaulHomes in the JIRA login screen. All seemed fine.
>
> Today however iansutton created a project and I was unable to browse it
> even though I was in the jira-users, jira-administrators and
> jira-developers groups. It got weirder when I created a new project as
> the lead - although I was able to create the project and the iansutton
> account could browse it I could not - I still able to administer the
> site though.
>
> Eventually it clicked and I logged out and logged in again using
> paulhomes (same account - different case). I was able to browse and
> administer. If I logged in using PaulHomes - I could only administer.
>
> Perhaps it would be good if you were able to prevent the initial mixed
> case user account in the setup process, disallow non-lowercase logins or
> convert the userid to lowercase during the login process.