[#6888] ticket:495 option to disable the send message form
[#6888] ticket:495 Store option in preferences, don't use extra field on User
[#6888] Added CSRF token and missing closing tag to user message pref form

Signed-off-by: Cory Johns <admin1@users.sf.net>
[#6888] Invert user message pref to clean up default case

Signed-off-by: Cory Johns <admin1@users.sf.net>