Removing the content load shield

 - Settings forms
 - Filtering of anchor and img tags
 - 'with_privacy' functions
Use the DDG image proxy for all embedded images.
Removing / amending CLS tests
Removing content load shield wrapper, removing calls from Postman.
Link images in comments to proxied URL.
Merge pull request #227 from jbarrett/deprecate-cls

Replace the content load shield.