Increase default STS_MAX_AGE from 30 days to 1 year to allow inclusion into HSTS preload list

* Firefox requires that any built-in HSTS preloads have a max-age
  of at least 18 weeks (10886400 seconds). Since that's already
  over 4 months, make the default 1 year (31536000 seconds).
  If this ever becomes a problem, a max-age of 0 can be used as a
  knock-out entry to override any built-in or existing browser
  settings.