Multi Image Picker Code Part 1

@vokalinteractive/ios-developers The vast majority of changes are xib and binary. Anyone have time for a review in the morning?
Doesn't seem to matter, because I can't get IB to use the layout anyway. I think it's because the flow layout has the sizing options available in IB, so IB uses that size and doesn't run the layout code…I think. But also, `UICollectionViewFlowLayout` isn't `IB_DESIGNABLE` anyway.