control point picker & list fixes

[Mike Runge]

Just a small addon, I forgot:

In the last versions it was not nessesairy to explicitely select the last set
point pair to delete it. If I set a pair of points and aft failed I just had
to click delete to remove the pair - the last pair was already selcted.

This behavior is gone with version of sep 07. I liked it, not only to delete
pair, where aft failed. It was comfortable as well to remove a mispicked
pair. Mispicking pairs can happen easily now with the new aft behavior,
because you loose overview about the whole picture when the first picked
point is zoomed in - e.g. with repeating structures (fences, laterns,
windows, etc.).

Or better:
Would it be a possible use for the back button to jump back to the last
situation, where the first point is already picked (and zoomed in) and you
just have to pick (replace) the second one? Is that feasable at all?

best, mike