add buttons to change orientation of even/odd pages - usecase for RADF scanners

I recently bought an Epson ET-5850 which works nicely with sane-airscan. The only thing I found missing was the awareness of duplex scans of the RADF showing every second scanned image upside down.

This PR extends the reordering dialog with 2 options, rotation either even or odd numbered pages by 180 degree which is much more convenient compared to rotating each sheet manually.

Alternative: Detect RADF, but I did not investigate that avenue yet.