Space del

I see constraint violation issues when deleting a space with custom content.
The reason is that the content items aren't deleted in the correct order. 

In short: I don't think that  http://jira.jcatalog.com/browse/WCM-251 is really fixed.

This branch contains a fix which works for me (although it's quite slow .-(( )

Look at commit 3a608d721a4cea38d8f6bcbe7f11628d44885a6 (the last one)