The next-node MAC address doesn't need to be unique in different
communities, so we can as well add a default value.

The SSID for the mesh network should be cryptic, otherwise some users will try to connect to that network and have a bad user experience.

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

Generate flashable images for the Archer C7 v2 with current stock firmware
again.

To set the region code, the GLUON_REGION variable must be set to "us" or
"eu" in site.mk or as a make argument.

Fixes #860

and add documentation

Fixes #823

Newer versions of Sphinx would break lines at the colons.

link to site-repo updated

Change the limit to match our recommendation in the site-example.

This commit basically does two things: it urges users always to use an own
git repository to manage the site configuration, and it removed all
mentions of "communities" from the "Getting started" page, as it was too
Freifunk-specific.

Other documentation pages (especially the site configuration docs) should
probably be adjusted as well.