Add class UserIdData and browser id cookie, use when voting

- Allow not-logged-in users to vote, use browser id cookie to track votes
- And browser cookie id and fingerprint database columns
Add back save/load vote tests.
Upgrade to ScalaTest 2.1

And fix compilation warnings by importing: org.scalatest.MustMatchers
but not: org.scalatest.matchers.MustMatchers.
Make it easy to count like/wrong/offtopic votes by parsing the HTML.
Add E2E test: VoteSpec, and remove Rating tests from AnonLoginSpec

Also remove pointless "iframe" flag.
Make votes somewhat secret

- Hide votes when logging out
- Don't load vote states for not-logged-in users
Start each E2E test with a new fake IP number

Otherwise, when run together with other tests, VoteSpec breaks
because comments become pending moderation.
Add VoteSpec to EndToEndSuite, comment out broken admin tests.
Merge branch 'topic-vote-fraud'.