the "next issue arrow" on view issue sits in the spot of the prev issue arrow

Early usability feedback, coupled with Penny's identification of the "Left/Right | Previous/Next mapping leaving a little to be desired", gives us an opportunity to fix the pagination control for

1. better understandability of "return to search" (Edwin)
2. a non-jumping affordance (Veenu)
3. a larger mousetarget (Jay)
4. a better natural mapping to J/K up and down progression through the issue list (Penny)

Edwin suggested we move the arrows to UP/DOWN rather than left right, which perfectly solves this problem. We'll add an explicit "back to search" link as well.