cs2cs: add --area and --bbox options to restrict candidate coordinate operations (fixes #2423)

[rouault]

CC @kbevers
This works exactly as with projinfo. Note that --area could potentially not give expected results, since it ends up being a bounding box. So if for example you have extent E1 and E2, and E1 is contained within E2, and you specify --area E1, then operations for E2 could still be used. But if E1 and E2 only overlaps, this should work as expected

[kbevers]

I can confirm that this works as I intended in the feature request. The caveat with smaller areas being fully contained in a larger area is of course unfortunate but in reality likely not a big issue. I am happy with this solution. Thanks!