Do not depend on the respondd-airtime module just to get the configured
channels. This removes the display of the frequency in addition to the
channel, as it is not readily available.

In addition, the translation string is improved to allow for text after
the channel number.

This code is usually running on an embedded CPU without FPU. In
addtition to its inefficience, the algorithm is also much harder to
understand.

Replace the logarithm formula with a simple loop.

This adds the wireless client count for 2.4GHz and 5 GHz radios to the
status page. Previously, only the total client count advertised by
the mesh protocol was visible.

This reverts commits
- caf2dd03.
- 07ebac6a
- 55eff45f

I accidentally pushed these commits as I had them lying around on a
dirty checkout I did testing on.

Fixes: #659
Signed-off-by: Martin Weinelt <martin@darmstadt.freifunk.net>

The field was accidentally removed during the status-page rewrite.

Fixes #1401

A downside of this behaviour is that the page does not work for IPv4-only
clients, as the redirect will always point at an IPv6 address.

Still, it seems like a good idea to enforce the redirect even from the IPv4
next-node address, as switching nodes while being connected to the status
page would lead to unexpected behaviour.

This new status page is significantly smaller than the old one. It always
loads its resources from the same host as the page itself, not requiring
cross-origin requests anymore.

It also uses the common i18n infrastructure of gluon-web.

Fixes #914