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 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

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