Refactor for Fennec Integration

 See Fennec integration bug https://bugzilla.mozilla.org/show_bug.cgi?id=1038843
    
    - Refactored StumblerService, moved bound usage to ClientStumblerService,
    this is not used by Fennec.
    - Restructure code by thread. Concurrency bugs are the highest-risk, and
    the code can be clearly organized by thread so future contributers can
    see at a glance where thread divisions are.
    - ensure that stumbler service init() happens on the correct thread, in
    MozStumbler, this is the main thread, in the Fennec service, this is on
    the service's dedicated thread
    - remove the use of the blocklists from Fennec.
    - changed uploading in fennec mode to only upload after a start intent.
    Need to ensure that when foregrounded, Fennec sends this message.