[modules] Initial module loading framework

Add a very simplistic framework for loading modules that query system
data. The user can provide a list of modules via an argument switch, and
the name of the module is used to look up a Python module that has to
have a class called "Module".

The outer framework (the outputs, in particular) then uses various query
methods of that class to construct a meaningful output.

bumblebee/modules/time.py

@@ -0,0 +1,7 @@
+import datetime
+
+class Module:
+    def data(self):
+        return datetime.datetime.now().strftime("%x %X")
+
+# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4