When importing XE XAR from an empty database, the import result is not properly displayed

See http://tinycoke.com/_6rm4qKJ12k2o/screen_shot_2010-01-25_at_7.02.08_pm.png

This is due to the loss of admin rights during the import process. Previous UI would redirect to "You are not allowed to view this document" type of error. Now the UI is AJAX the redirection can't be made.

A solution is to display a warning with a text in this spirit :
"You have imported XWiki Enterprise default set of documents. From this point, you can for example visit the home page of your wiki. To continue administer the wiki, you will first need to authenticate"