core/legal-info: Add package dependencies with licenses to the manifest

This adds one column to the legal-info manifest table. It contains the
dependencies of the given package and their licenses. This information
is useful when assessing license compatibility of the packages and
their libraries.

An example of the content of the new column for the MPD package is
shown below:

    "alsa-lib [LGPL-2.1+ (library), GPL-2.0+ (aserver)] boost
    [BSL-1.0] libid3tag [GPL-2.0+] libmad [GPL-2.0+] libogg
    [BSD-3-Clause] libvorbis [BSD-3-Clause] libzlib [Zlib]
    skeleton-init-common [unknown] skeleton-init-sysv [unknown] sqlite
    [Public domain] toolchain-external-linaro-arm [unknown]"

[Credits to Yann E. MORIN <yann.morin.1998@free.fr> for suggesting a
few simplifications.]

Signed-off-by: Michal Sojka <sojka@merica.cz>
Tested-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Reviewed-by: Luca Ceresoli <luca@lucaceresoli.net>
Tested-by: Luca Ceresoli <luca@lucaceresoli.net>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>