luci-app-dawn: Implement in JavaScript

This commit re-implements luci-app-dawn in JavaScript, removing the older
lua implementation. Besides a 1-to-1 port, there are some
changes/improvements:

* In both the network overview and the hearing map, replace MAC addresses
  by host name if known.
* In the hearing map, the table is sortable. If the same client is
  connected to multiple access points/frequencies the MAC/host name is
  listed twice, whereas in the lua implementation the second MAC address
  was empty to show it was referring to the same client. This means the
  table can be sorted on any column, and the information remains correct.
* The view in the network overview is a bit different. This table is not
  sortable, because LuCi doesn't seem to like a table inside a table for
  sorting.
* Align the column names between the network overview and the hearing
  table.
* Add tooltips for abbreviations in column names.

Signed-off-by: Daniel Vijge <danielvijge@gmail.com>