Bug 1072181 part 1 - Use developer-focused branding and configuration for aurora. r=gavin, f=rstrong

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extra : rebase_source : 2752b788cc1fdcf60aed7907162c1e214623543d
Bug 1072181 part 2 - Use new assets for the aurora channel. r=gavin

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extra : rebase_source : cbddebecf0bc46479a77b73305cf7889b83633b9
Bug 1072181 part 3 - New Aurora channel prefs r=paul

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extra : rebase_source : 9998025d99157cb150e87a47e18fe145b38ecbc2