containers as index 'documents'

[Andy Altepeter]

If you add a folder (or presumably a publication) with id of 'index' (the index
document of a container), it appears twice, once in the '0' location, and once
in it's real location. My first thought was to suggest raising this as an
error, but someone may have an index container that is a gallery (containing
images), so that one would make sense. Unless there was an "allow_as_index"
function...

[Kit Blake (kitblake)]

I noticed on a site where 'index' is a Ghost Folder. Somewhat dangerous, as I
almost deleted the 'second' one.

[Sylvain Viollon (thefunny)]

- The name chooser should not permit to pick index as an id for a container

- get_default method should pay attention not to return a container.

Those cases should be tested.

[Sylvain Viollon (thefunny)]

This is fixed.