Comment 0 for bug 921061

Following the design specifications from:

https://docs.google.com/a/canonical.com/document/d/1ILTJDiDCd25Npt2AmgzF8aOnZZECxTfM0hvsbWT2BxA/edit?ndplr=1&pli=1#heading=h.jztfy8l5q9v5

The category headers in Gnome Control Center must be reworked to include an icon, slightly bigger font and an horizontal divider between categories.