Enable searching of Docker Registry

Test Plan:
Launch a stack, upload an image, then try:
`curl -s <registry>/v1/search?q=<keyword>`

Reviewers: merkkila

Reviewed By: merkkila

Subscribers: tberman, justin, stephan, serdar

Differential Revision: http://phabricator.thefactory.com/D2857
Add capabilities param to create-stack example
Merge remote-tracking branch 'upstream/master'

Conflicts:
	docker-registry.json