Patch for jpg orientation from photo or uploader

[slup]

When uploading pictures from my mobilephone, chyrp did not respect the EXIF orientation and showed the pictures with the wrong orientation.
This change rotates the uploaded (JPG-) image(s) to the orientation given in the EXIF information.

[xenocrat]

Hello there,

Thanks for taking the time to submit this PR.

Modern web browsers read and respect EXIF orientation metadata when displaying images, so I assume the root of your problem is with the way thumbnails are rendered using the thumbnail filter in Twig and/or ThumbnailFile class. I've decided not to merge this PR because I don't like the idea of modifying the source image during post creation; instead I'm going to add orientation support to the ThumbnailFile class. Your code will be very helpful for my implementation, so thank you again for submitting it!

I've created issue #282 to track this. I'll also leave this PR open for now.