[themes] Add "cycle" theme capability

It is now possible to add a list of theme configurations in the
"default" section called "cycle". These configuration items will be
cycled through module by module. to create "alternate style" effects.
This is *only* possible in the "default" configuration part, but any
module-specific configurations still take precedence.

Also, removed the capability of per-widget themes. That simply
complicates things and probably doesn't really bring any benefits.

bumblebee/modules/battery.py

@@ -2,8 +2,8 @@ import datetime
 import bumblebee.module
 
 class Module(bumblebee.module.Module):
-    def __init__(self, theme, args):
-        super(Module, self).__init__(theme, args)
+    def __init__(self, args):
+        super(Module, self).__init__(args)
         self._battery = "BAT0" if not args else args[0]
         self._capacity = 0
         self._status = "Unknown"

bumblebee/modules/time.py

@@ -2,8 +2,8 @@ import datetime
 import bumblebee.module
 
 class Module(bumblebee.module.Module):
-    def __init__(self, theme, args):
-        super(Module, self).__init__(theme, args)
+    def __init__(self, args):
+        super(Module, self).__init__(args)
 
     def data(self):
         return datetime.datetime.now().strftime("%x %X")