Fixes #414

Allows weird release numbers, models and site names, and prepares support
for pretty hostnames.

When rebooting the node in config mode, currently the fastd key is
forcefully displayed in a fixed format. This is confusing in communities
where fastd accepts all keys and no key submission is needed.
Furthermore, some communities might want to personalize the display of
the key (see #387).

This patch moves the displaying <div> from the package's lua file to the
translation files of the sample site configuration and mentiones the
change in the release notes.

This commit splits gluon-config-mode into several, mostly independent
packages.

* gluon-config-mode-core: basic functionality (required)
* gluon-config-mode-hostname: hostname field
* gluon-config-mode-autoupdater: show when autoupdater is enabled
* gluon-config-mode-mesh-vpn: fastd vpn configuration, bw limit
* gluon-config-mode-geo-location: geo coordinates
* gluon-config-mode-contact-info: contact info field

The package gluon-config-mode has been removed. You need to replace
it with these packages (or any subset of them) in site.mk:

* gluon-config-mode-hostname
* gluon-config-mode-autoupdater
* gluon-config-mode-mesh-vpn
* gluon-config-mode-geo-location
* gluon-config-mode-contact-info

Note: It is not possible to deactivate the autoupdater in config mode
anymore (expert mode will still allow it). Instead, a message is shown
in case the autoupdater is enabled.