Also simplify the local_node.peerdns setting.

Nothing outside the config mode depends on luci-base anymore.

We also make use of the boolean support of simple-uci to make scripts
clearer.

The maintenance overhead doesn't justify keeping this old stuff anymore.

Rework init script to additionally join a ff05::... multicast group on the mesh-wide interface.

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

Fixes #1022

Fixes a build issue when switching targets.

Setting DEVICES will also suppress cleaning the package directory,
improving incremental build speed.

A lot of our code does not actually work with other prefix lengths.

Fixes #1014

Add gluon-dns-config: a package that enables the node to be used as DNS cache

The ar71xx-tiny target sets CONFIG_CLEAN_IPKG, which would delete opkg
control files required for user creation. Fix image generation and the user
creation script.

Fixes #1012

Fix an exception breaking the page.