Removed unused 'useragents.ini' file

The file has been obsolete since 2aeecd519 (migration from
browscap to ua-parser, moving useragent configuration from
the ini file to localSettings.json)
Page: Always link to HTTPS for sites that support it

Protocol-relative urls are nice, but if you're serving a page
from HTTP and linking to GitHub or Twitter they'll just redirect
you to HTTPS.

Might as well link to that directly instead of serving redirects.