Fix creation of user for use with CAS

Th user has already been created by the CAS authentication system.  However, it
has not been initialized yet so it should be initialized.
Fix the subwiki creation by a logged user

A logged user has not the rights to create a subwikis so expose the deeper API
which bypass these rights to create the subwiki when the user wants it.
Fix a problem with the check of current user

The current user should be checked directly from XWiki functionalities (not
based on the CAS authentication).
Hide documents in templates

These hidden documents should not be displayed in livetable since they are
needed for development.
Replace 'createNewObject' with 'newObject'

Both functions from the 'Document' class are making the same operation but the
first one is returning the number of the object and the second is returning the
object itself.
Make hidden some created pages

The pages about the initialization of the user and the attribution of a group
should not be accessible to the user (since they are not intended to be
modified).
Create a macro for the collaborative spaces

This macro displays all the documents that have been created by the user.  It is
a slight modification of the original 'documents' macro but with a filter for
some specific spaces and pages.