Introduce localuser interface for applications

This change make use of nss-localuser hostname
family (see https://git.automotivelinux.org/src/nss-localuser/)
to separate applications and users, each running its
own IP address and hostname.

The intended behaviour is to use existing browser policy to
ensure privacy of applications and users.

Bug-AGL: SPEC-2968

Change-Id: Ie1a3c7331fd43e8747afae2cd338df461bac1454
Signed-off-by: José Bollo <jose.bollo@iot.bzh>