Print feature for course members list element

The course element "members" shows the users of a course. In a scenario with classes and teachers, this is very handy and can replace the printed version of a so-called "Klassenspiegel". However, when printing the online view of the members course element, the formatting is not very usefull and there are additional information that should be on a printed version.

This issue is about adding a specific print option to the members course element:

Todo

• Add print button to run view (next to mail button)
• Render a print view with special print CSS and markup, similar to the print view in the test statistics
• Add a print title
• Add the course name as sub-title
• Use the larges user images we have, use img tag and not css background-image to support printing
• Use other user property context to display other user properties in the print view than in the online view