generate list of license information for packages

Many packages define already metadata about their license (PKG_LICENSE),
but this is only included in the ipk files.

This change allows to create the information also on the build-host,
to get an overview on the used licenses.
In the full list, also all packages without this info are shown

Signed-off-by: Thomas Langer <thomas.langer@lantiq.com>

SVN-Revision: 43070