(bug 13015, bug 18347, bug 18996, bug 20473, bug 23669, bug 28244) separate the password-reset request dialogue from SpecialUserlogin.

• Refactor with all the latest bells and whistles
• Allow wikis to enable resettting by entering an email address (bug 13015). This is currently an unindexed query, but it is disabled by default so no immediate problem.
• Allow resetting to be disabled entirely (bug 20473).
• Don't send registered users' IP addresses in the emails (bug 18347)
• Check that a user is not globally blocked before letting them send messages (bug 23669)
• Display a more useful error message when an account exists globally but not locally (bug 18996).