Preferences: new preference for ignoring EXIF orientation flags

Many thanks to contributor Cat for this suggestion / bug report.

Some cameras (and/or software) may rotate images without rewriting the
corresponding EXIF orientation tags.  This presents a particular problem
during batch conversion, as the resulting images will be (correctly!)
auto-rotated by PhotoDemon, resulting in double-rotation.

Unfortunately, there is no way to auto-detect when other
hardware/software has screwed up these tags, but this new preference at
least provides an emergency override.