Add a `<Report format> warnings per project` portlet. It would be nice to have one generic portlet entry which allows to configure

• the display name of the portlet
• whether zero warnings projects should be hidden
• the type of report format (CheckStyle, CPD, SpotBugs, ...)
• the column content (severity, category)

By having only one generic portlet entry we would avoid to overload the dropdown component with too many entries.