Post Settings: Default to on

[jasmussen]

Splitting this out from #450: post settings should be shown by default. You can then dismiss them if you like, and when #450 is in this choice will be cookied. But the out of box experience should be showing post settings.

Note: this behavior likely needs to be reversed if you load the editor from your phone. In this case, post settings is a modal toggle, and needs to start off. On mobile, in other words, your choice to open or close should not affect whatever setting you've cookied on desktop.