Re-add the NIC module with all its functionality (hopefully...).
This introduces a new concept: Instead of having separate queries for
critical and warning (which really are just another set of states), a
module can now return a list of states for each widget. All the state
information is then merged together into a single theme. So, for
instance, the NIC module can return a state saying "critical -
wlan-down", which applies the theme information for both "critical" and
"wlan-down".
see #23
Make the format string of the datetime module configurable using the new
parameter() method in the module.
Also, restructured the setting of the config information a bit so that
the parameter() method can be used in the constructor of a module.
see #23
Add a helper function that lists all existing modules and modify the CPU
module test so that it now generically iterates all available modules
and tests their widgets.
see #23
