Fix urls_start_arg for defacl, improving error messages
Support canned ACLs in tab completion for ACL commands.
4.7 Release Notes
Update CHECKSUM and VERSION for 4.7 release.
Added -I flag to rm command to allow stdin input for object URL args.

CLI change based on thobrla's review

Fixed command spec issue and extended unit test to check -I over multiple buckets

Fixed stdin caps consistency. Made -I cmd exception more specific.
Minor doc fixes