Improve CE to EE ROI calculator

There are two small changes we can make to the CE to EE ROI calculator to greatly improve the usability of the page.

• Group features by product capability (i.e. all issue tracking features in one section)
• Make it possible toggle the entire section of one product capability on or off (i.e. add a checkbox that would deselect all of the issue tracking features if a user does not want to get the ROI of using GitLab's issue trackers. This is a realistic scenario for users who may want to stick with their existing issue tracking solution and right now they would have to uncheck every box manually.)