Add styles and options for comments

A comment will be placed under the heading, this commit provides
the css and the options in the default.ini
Use option from default.ini

The heading will only be displayed if the option is set in the
default.ini (on default, this will be set to false)
Add function to retrieve a comment

Note: Use of the option in the default.ini whether to display the comment
will be implemented in a later commit.
Rework phtml for list to display headings