support for the other 4 exif orientations

[jkmcnk]

I added support for the yet unsupported exif orientations: flip {h,v}, trans{pose,verse}. thought I might as well contribute something back. so, here's the relevant code for your consideration.

you can test it with the exif orientation sample dataset here: http://k00.fr/kvfvy

best, j

[davemorrissey]

Looks interesting, did you do this because you needed the feature? Until now I don't think anyone had asked for it. It'll need some thorough testing which I don't have time for at the moment but I'll come back to it.

[jkmcnk]

yes. as far as testing goes, it was (and is being) tested with and without tiling, in a pan and zoom setting, in the android client for our storage service on a variety of devices, but I do suppose a more systematic approach to testing would be nice. ;) anyhow, glad to fix any issues that might arise.

[davemorrissey]

I don't plan to merge this but I'll leave this PR open so others can use this branch if they need this support.

[perracodex]

I've tested this pull request for all possible Exif orientations, and image rendering works correctly, but panning fails for flip vertical / horizontal, transpose, and transverse.
The issue is in the onFling callback, the velocities should be inverted + adjusted for these cases.