Add popover to confidence and severity labels with brief description

From this thread: https://gitlab.slack.com/archives/C8S0HHM44/p1570029914443100

Hi folks.. When demo’ing the security dash to customers I often get asked about the “undefined” hits in the results. Why is this undefined? Can it be hidden? Renamed? Fixed? In the customers eyes, its broken.

Problem:

How might we inform users of our definitions for the terms we use for severity and confidence?

Solution 1:

Add a popover message when a user hovers over the severity or confidence labels within the vulnerability list.

The popover can contain:

Severity popover:

• Severity level
• Brief description
• Link to documentation

Confidence popover:

• Confidence level
• Brief description
• Link to documentation