[core/theme] Add option to override iconset + add experimental icons

Add an option to load a user-specified icon theme (which will override
the theme's icons).

Also, commit a first version of a set of icons from the ionicons set
(see http://ionicons.com/).

see #252

bumblebee/config.py

@@ -59,6 +59,8 @@ def create_parser():
         help=DEBUG_HELP)
     parser.add_argument("-f", "--logfile", default="~/bumblebee-status-debug.log",
         help="Location of the debug log file")
+    parser.add_argument("-i", "--iconset", default="auto",
+        help="Specify the name of an iconset to use (overrides theme default)")
 
     return parser
 
@@ -91,6 +93,10 @@ class Config(bumblebee.store.Store):
         """Return the name of the selected theme"""
         return self._args.theme
 
+    def iconset(self):
+        """Return the name of a user-specified icon-set"""
+        return self._args.iconset
+
     def debug(self):
         return self._args.debug