feature (stats): Weekly and monthly goals.

Add a new editing interface for weekly and monthly goals.
Textual viewing interface is currently a stub.
Add `month_timestamp` and `week_timestamp` lion properties.

bot/modules/stats/__init__.py

@@ -4,3 +4,4 @@ from . import data
 from . import profile
 from . import setprofile
 from . import top_cmd
+from . import goals