Bug 1073240 - update Firefox's default theme icon, hide menu on non-default themes, r=jaws

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extra : rebase_source : 3651f3e80cf537c365a6ab4a0659221fb6d50d4b
Bug 1070888 - set position and flip attribute so lightweight themes panel in customize mode opens correctly, r=jaws

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extra : rebase_source : 9a34be6c24641103c7c0b70573322b2defe0c90d
Bug 1076252 - [10.10] disabled default button shouldn't get white text on yosemite, r=jaws