license: add SPDX tags to all projects that have appropriate licenses

Signed-off-by: Eric Schultz <eschultz@prplfoundation.org>
libnetconf: update package to version 0.9.0

Signed-off-by: Jiri Slachta <slachta@cesnet.cz>
freesub: add package

Signed-off-by: Luka Perkov <luka@openwrt.org>
freesub: update to latest git HEAD

Signed-off-by: Luka Perkov <luka@openwrt.org>