[modules] Add DNF supervision module

Add a module that periodically (by default, once every 30min) calls
"dnf updateinfo" and evaluates the results to report the number of
bugfixes, enhancements, etc.

If there's either too many pending updates, or at least one security
update, the module goes critical.

bumblebee/themes/solarized-powerline.json

@@ -35,6 +35,15 @@
 	"disk": {
 		"prefix": "  "
 	},
+	"dnf": {
+		"prefix": "  ",
+		"states": {
+			"good": {
+				"fg": "#002b36",
+				"bg": "#859900"
+			}
+		}
+	},
 	"pasink": {
 		"states": {
 			"muted": {