chsmack: adding options --remove and --dereference

Using the option --remove (-d), chsmack is able to delete
the security tags specified or the all if none is set.
(See issue #28).

The option --dereference (-L) indicates that the symbolic
links have to be followed, that is their target that will
be altered.

Change-Id: I33d1a4824f7f3f10b0ba3d621a311c6e665137e6
Signed-off-by: José Bollo <jose.bollo@open.eurogiciel.org>