make paste focuses the pasted cell
make paste focuses the pasted cell

This is to make paste behave in the same manner that insert cell above
and below currently work (inserting a new item causes that item to
receive focus).

This solves a problem where, if a user pastes below a cell whose bottom
edge is below the current viewing area, they have no indication that any
action has occurred. The same applies for paste above a cell whose top
edge is occluded.

ipython/ipython,ipython/ipython