Expand archive_info to include ctime, vmid and is_std_name

Expand archive_info to include ctime, vmid and is_std_name

where 'is_std_name' shows whether the backup name uses the standard naming
schema and most likely was created by our tools.

Also adds a '^' to the existing filename matching regex, which
should be fine since basename() is used beforehand.

Signed-off-by: Fabian Ebner <f.ebner@proxmox.com>