Bug 1042135 - Change three-state DNT back to two state and update text.  (r=dolske,jst,mcmanus)

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extra : rebase_source : 2cc113eb167b83ded586b36380bb444a827f0084
Bug 1042135 - Change three-state DNT back to two state and update text in Fennec. (r=liuche)

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extra : rebase_source : 4cb863131033da3cbbccb80751264d324aeda3e7
Bug 1042135 - Update Directory Links Provider to use only the dnt.enabled pref after removing the dnt.value pref. (r=adw)

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extra : rebase_source : 350e99d270e18f497f69a77672557a18ac66ef6d