Added exif rotation to the Android PictureChooser plugin

Added methods to properly rotate an image according to the exif rotation
data contained in the file when loading or taking a new picture.
Merge branch 'v3.1' of github.com:jsmarcus/MvvmCross into v3.1
Follow up to #627 - added a pokemon handler for now - it will drop back to the resampled/scaled picture if the exif code fails on some Android variant.