[modules/progress] improved autohide functionality

Simplify the previous autohide functionality by adding a flag that lets
a module (e.g. progress) indicate that the current state should be
"revealed" (not auto-hidden).

This vastly simplifies the implementation.

see #835

bumblebee_status/modules/contrib/progress.py

@@ -101,7 +101,7 @@ class Module(core.module.Module):
 
     def state(self, widget):
         if self.__active:
-            return "copying"
+            return ["copying", "no-autohide"]
         return "pending"