* doc/en/user-guide/authentication_conf.txt: New file. Authentication configuration file documentation.
* doc/en/user-guide/configuration.txt: Slight modifications, add authentication.conf reference.
* doc/en/mini-tutorial/index.txt: Fix make docs warning.
* doc/developers/authentication-ring.txt: Small cleanups noticed during doc/en/user-guide/authentication_conf.txt redaction.
* bzrlib/transport/http/_urllib.py: (HttpTransport_urllib._perform): Use a dict() instead of {} syntax.
* bzrlib/tests/blackbox/test_whoami.py: (TestWhoami.test_whoami_branch): Delete BZREMAIL related tests.
* bzrlib/config.py: (Config.username): BZREMAIL deleted, has been obsolete for more than a year. (AuthenticationConfig.__init__): Review feedback, since keeping a callback as an attribute is useless, call it now and keep the filename itself as an attribute. (AuthenticationConfig.get_credentials): Use a dict() instead of {} syntax.