post tooltips: add disable option (#3689).

* Add "disable post tooltips" account setting.
* Add back title attribute for when fancy tooltips are disabled.

app/logical/anonymous_user.rb

@@ -277,6 +277,10 @@ class AnonymousUser
     false
   end
 
+  def disable_post_tooltips?
+    false
+  end
+
   User::Roles.reject {|r| r == :anonymous}.each do |name|
     define_method("is_#{name}?") do
       false