Move oauth.ini to config.ini and update README
Refactor
[#25] Handle images with EXIF orientation tag correctly

- The crop coordinates are rotated to match the orientation of the image. The EXIF orientation tag is kept and the image is not rotated.
- Since browsers may ignore the EXIF orientation tag for images shown in web pages (tested in Chrome and Firefox, both ignored it), a normalized (rotated) thumbnail for viewing is created both for the original image and the cropped version.