username+password rules, undo menu-fix from last commit, bit of css

disabled autocorrect, autocomplete, autocapitalize and spellcheck on all username, password and email fields
changed _get_input rule 'strict' to a-zA-Z0-9_ and introduced new rule superstrict which is a-z0-9_
all usernames are now superstrict and passwords are strict - defined in js/config.js username_rules and password_rules
added slight right margin to checkbox labels in pageedit_privileges
removed menu fix as it concealed sidemenus when user browsed a page in the sidemenu