WikiGrok A/B test dry run

* Create the wikiGrokUser class, which encapsulates the state of a user
  that might be entered into the test
* Create the WikiGrokAbTest class, which controls whether or not a user
  is eligible to enter the test and, if so, which version of WikiGrok
  they'll see

Change-Id: If038f131a78e171479db6a18c311940d79c42277
i18n: Remove unnecessary quotation mark

Change-Id: I34632ba0f16497e1781f0bc89ea1aef586f1b459
Merge "WikiGrok A/B test dry run"