Bug 850600 - Refactor FirefoxAccounts. r=rnewman

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https://github.com/mozilla-services/android-sync/commit/9acbc565be9e1065e3e4f1d62f482a5de02a6323
Author: Nick Alexander <nalexander@mozilla.com>
Date:   Fri Apr 18 11:30:26 2014 -0700

    Bug 850600 - Part 0: Refactor FirefoxAccounts.