[MDC-825] simetbox-openwrt-luci: add renew creds button to about page

[MDC-825] simetbox-openwrt-luci: add renew creds button to about page

Rework the "about SIMETBox" page to add the "renew credentials"
(register) button that we also added to the SIMET2 results page.

While at it, rework the auto-upgrade button and page table layout.