Update changelog
Don't load the exercises' app's JS in the muscle overview template
Correct exercise image field description
Don't show a big main image in the exercise detail view

While this is useful when there are many images for an exercise (e.g.
a sequence, etc.). At the moment the exercises will have 2 or, at the
most, 3 images. This makes the page design more balanced.
Generate all thumbnails when uploading a new image
Fix some problems with the tests when running on some systems
Check for correct permissions when accepting or declining exercises
Add license and author fields to exercise images
Reduce the size of the muscle diagram in the exercise view