[MDC-824] simetbox-openwrt-luci: add SIMET2 results page

[MDC-824] simetbox-openwrt-luci: add SIMET2 results page

Add a page to the menu with the iframe for the SIMET2 results frontend,
using the VTK token and agent-id as the credentials.

We don't have to handle the "missing VTK" or "invalid VTK" cases, this
is done by the frontend which will show an appropriate message.