JPEGMetaData: support orientation

[mickleness]

The ImageFileDirectory is parsing an orientation, but it's getting it wrong. Early research suggests we're getting 4 bytes like: 0 0 0 6. We're reading a 2-byte short from the first two bytes, so we get back 0. If we read the last two bytes we get 6 (the correct value).

We need to read up on parsing and see if all shorts are similarly broken.