rose edit: fix pluggable metadata for within rosie go

Currently, <code>rosie go</code> will fail nastily if no project is defined in the new suite wizard and then the project is altered in the subsequent page. This is due to an incompatible piece of code in the config_editor.main module (def refresh_metadata...).

The metadata that makes altering the project nicer (as well as the other options) was also not being picked up, which is now fixed. The rose.macro.add_site_meta_paths, etc, is usually invoked at the bottom of config_editor.main, but won't be in rosie go mode (pluggable).

When the metadata is reloaded, the current selected variable widget (if any) should now still be selected in the open page.

@arjclark, please review.