do not strictly resist on Fedora's OpenID

To allow users use multiple authentication options concurrently
(e.g. simply password/hash auth in future & Fedora OpenID), we
need to keep single and unique username in our database.  To allow
that, transform the 'openid_name' column from 'user' table into
simple 'username'.
support for kerberos authentication

The krb auth method is aimed to be self-standing auth method, but
also can be used as alternative way how to connect to Copr
in parallel with Fedora OpenID authentication method.

The OpenID is currently still the default and the Copr 'username'
is bound to OpenID username (such usernames must match);  this
should be fixed in future so that the Copr user is 1:N mapped to
OpenID credentials (similarly like the krb is).
[frontend] project search update after patch