[config] Allow parameter passing via commandline

Allow the user to specify arbitrary configuration parameters from the
commandline and evaluate those in the modules (and elsewhere). Re-enable
the CPU module as a first showcase of this functionality.

bumblebee/themes/solarized-powerline.json

@@ -18,6 +18,7 @@
 		"bg-warning": "#b58900",
 
 		"default-separators": false,
+		"separator-block-width": 0,
 		"separator": ""
 	},
 	"date": {