doc2dt should not rely on desktop
Handling of "desktop coordinates" should not depend on SPDesktop, which isn't available in certain situations, like:
- Opening of a document which creates a new window (desktop not created yet)
- Command line processing (desktop never created)
Known issues (with /options/yaxisdown="0"):
- Handles of 3D boxes initially imported wrong (fixed by "File > Revert")
- Guides initially imported wrong (fixed by "File > Revert")
- Raster image position wrong (#337 (closed))
The problem would be solved by moving doc2dt and related methods to SPDocument, which always exists.