Add a troubleshooting section to the shell.

shell/README.rst

@@ -38,6 +38,17 @@ Example session:
     res.partner(7, 51)
     
     
+Troubleshooting
+===============
+If the command does nothing, or if you have the error
+
+    Usage: odoo.py [options]
+
+    odoo.py: error: unrecognized parameters: 'shell'
+
+it is surely because of the order of the parameters. Try the following:
+
+    $ ./odoo.py --addons-path=<your_path1>,<your_path2> shell --config=<your_config_file> -d <dbname>
 
 Bug Tracker
 ===========