Upload to cloudinary folder and image caption

I added the options to 

- upload images to a cloudinary folder
- use original filename
- set unique filename

and added captions to the cloudinaryimages ImageSchema and form.jade

cloudinary settings:

keystone.set('cloudinary foldername', 'test-folder'); // enable "Auto-create folders" in cloudinary
keystone.set('cloudinary use_filename', true);
keystone.set('cloudinary unique_filename', false);