unspoorted browsers trying to access the login mask will be forwarded to
an info page.
The info page shows that the browser is not suppoted and hints the smallest
supported version of their current browser.
As it works best and might prevent some support calls, I added an hint
for chrome as the favored browser by OpenSlides (debateable)
To update/downgrade the supported versions, simply edit the enum in the
service.
If we cannot detect the browser, we assume it was supported.
