Configurable callback when selecting files in Popup

[dkoenigroer]

We have a CKEditor and someone configured the browser url settings to

"filebrowserBrowseUrl": "/admin/filer/folder/213/list/?_pick=file&_popup=1".

But the Filer expects a FilerField-Target and is only able to return a File-ID.

So a nice feature could be to add a get param with a field name where to put the value in (which is already there but not modifiable) and a field name which value will be returned.

"filebrowserBrowseUrl": "/admin/filer/folder/last/?_pick=file.url&_to_field=%(to_field)s&_return_value=url",

So here we tell the popup tp return the file url instead of the file.id. The _to_field is a placeholder here. i am not sure if the opener winodw knows the field automatically.