Fixed: tests, cursor position in the source file may have moved
Fixed: tests, doesn't guess only from file extension anymore
Updated: ArchivePack decompressors now retrieve the name from the member

- If the ArchivePack has a single file that will be streamed, the
  realname is retrieved from the member
- The filename is also added in the list compressions of the archive
  instance
- Now it is tested (except for a specific case of p7zip, that does not
  work)