Support EXIF orientation for network JPG/TIFF

Uses commons-imaging to determine orientation (only if it's on the classpath, it's an optional dependency).  Tests intentionally omitted for now, happy to add them if you want this feature.

Since commons-imaging is still at 1.0.0-SNAPSHOT I had to temporarily add the Apache snapshot repository but this API hasn't changed since it was brought into commons.
I was thinking about adding the dependency for Sanselan and then using reflection to use either Sanselan or Apache Imaging, whichever is on the classpath.  Not sure how close they are to final release for commons-imaging.