Progress: continued work on user settings

Progress: continued work on user settings

Remove meaningless trailing semicolon.
Organize user page handler constants in alphabetic order.
Add missing user page handler constants, classes, and files.
Use static:: in place of self:: (more to come on why in a follow up commit).
Move the user_view.php contents into user_settings.php and have the user_view class extend the user_settings class.