rotate images regarding exif information

This should fix #973 and #331.

I used the Exif class from `com.android.gallery3d.data` from [Android 4.2.2r1](http://grepcode.com/file/repository.grepcode.com/java/ext/com.google.android/android-apps/4.2.2_r1/com/android/gallery3d/data/Exif.java?av=f). The newer Android versions are using a more complex class to get the exif parameters, but we just need the orientation, so I chose the one from 4.2...

I don't know if its okay to put the google code just like that in the source directory?