new variable 'unlink'

Solve issue #11 by allowing the use of --unlink wget option

Use the following line in mirror.list to enable it:
 set unlink 1
Merge pull request #14 from dr4Ke/mirror_to_hardlinked_directory_2

Use --unlink option with wget to mirror to hardlinked directory
Merge branch 'master' of github.com:apt-mirror/apt-mirror

Conflicts:
	mirror.list