Inbox tab redesign

[rnystrom]

Alongside #491, I'm going to update the inbox and remove the segmented control to switch between unread and all. Instead, I'm going to default the list to be only unread and add a left nav item for "All" (or maybe "Archived"?). This will:

• Simplify the VC
• Make toggling read/unread states bubbling up to the VC way simpler (e.g. swipe action)
• Make the app icon badge # match exactly what is shown on launch (same network request)
• Simplify the UI (no seg control)

[rnystrom]

I think I’m going to try out iOS 11 nav style and put the search bar in the nav item too.

Not totally sure how this will look iOS <11 tho.

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[BasThomas]

FWIW, you can of course check iOS 10 on the iOS 10 sim.