Settings Validation: don't allow cron to less than 5 minutes.
Sanitize selected_sitegroups before saving.
Stop saving syn_transport_mode; it's useless.

Show the client type on the "Sites" list screen.

fixes #14
XML Client: custom nodes should be under a separate key in the node_config to avoid confusion with other keys.
Pull XML: Remove get_guid method.

It's not really necessary since the XML has the GUID and our save process will determine whether the post is new or not. It was also changing the GUID to the ID every time, which was probably breaking stuff.