Add, edit, and remove, all edit the core model of runtime paths in this preference page. Also, the preference page is often closed and re-opened when this doesn't need to happen.

Possible fixes are

1) to ensure NO ONE saves a model until performOK or performApply is called,
2) keep track of if the page is dirty or not
3) show a dialog when clicking 'link' on a dirty page asking to save and re-open the page