ACL management : default behaviour

[Joacchim]

The acl are still not managed within the application :
Everything is created as a Canned ACL : PRIVATE

By default, the application should at least reproduce the canned_acl, or in case of failure, fallback to PRIVATE by default.

[Joacchim]

Improved by commit : 158acd4
158acd4

The canned_acl is now reproduced as much as possible, though only 4 of the 6 available canned_acl are identified.
The code still lacks the identification of BUCKET_OWNER_READ and BUCKET_OWNER_FULLCONTROL, because
of a lack of concrete examples of ACL XML.