The fastd_mesh_vpn site.conf section is renamed to mesh_vpn.fastd.

This was introduced in ffhh-packages at https://github.com/freifunkhamburg/ffhh-packages/tree/master/gluon-config-mode-reboot-ffhh

_translate() will return nil when no match is found.

Add missing trailing `,` in simple_tc section and change the order of ingress and egress to default format used by Gluon.

These devices don't have unique MAC addresses with OpenWrt/LEDE at the moment
(see #993).

Fixes #961

* use tabs instead of spaces
* use jsonfilter for speed

propose to make uci commit more specific to minimize unwanted changes in other temporary written config files like wireless ssid (in some offline changers)