[modules] Add module-specific configuration

Big oversight in my previous commits: Widgets need to be able to have
specific configurations (i.e. the path for different instances of the
"disk" module has to be different).

To account for that, it is now possible to assign an "alias" to a module
instance using ":" (for example: -m "disk:home"). This alias is then
used for the configuration parameter resolution automatically, for
example:

-m disk:home -p home.path=/home

As a consequence, parameter names in the module code are now relative to
the module, which means: shorter!

bumblebee/config.py

@@ -35,6 +35,23 @@ class print_usage(argparse.Action):
                 80, initial_indent=self._indent*2, subsequent_indent=self._indent*4)
             print ""
 
+class ModuleConfig(object):
+    def __init__(self, config, prefix):
+        self._prefix = prefix
+        self._config = config
+
+    def set(self, name, value):
+        name = self._prefix + name
+        return self._config.set(name, value)
+
+    def parameter(self, name, default=None):
+        name = self._prefix + name
+        return self._config.parameter(name, default)
+
+    def increase(self, name, limit, default):
+        name = self._prefix + name
+        return self._config.increase(name, limit, default)
+
 class Config(object):
     def __init__(self, args):
         self._raw = args
@@ -69,7 +86,11 @@ class Config(object):
         return self._args.theme
 
     def modules(self):
-        return self._args.modules
+        result = []
+        for m in self._args.modules:
+            items = m.split(":")
+            result.append({ "name": items[0], "alias": items[1] if len(items) > 1 else None })
+        return result
 
     def _parser(self):
         parser = argparse.ArgumentParser(description="display system data in the i3bar")