add registry to amp with HAProxy reverse proxy

[freignat91]

Add registry as a service

Test:

• pull swarm all images (should have registry:2 in the list): ./swarm pull
• start amp swarm: sudo ./swarm start
• create or pull an image for instance: docker pull alpine
• tag it: docker tag alpine localhost:5000/alpine
• push it: docker push localhost:5000/alpine
  image is pushed in the amp registry going through HAProxy
• verify you can pull it: docker pull localhost:5000/alpine ,having this console message: Image is up to date for localhost:5000/alpline:latest
• make install (rm -rf vendor and glide install, if needed)
• amp push localhost:5000/alpine -> push the image using amp command

[bquenin]

Tested and working

[generalhenry]

Failing on docker for mac in service mode, working in run mode.

[generalhenry]

Failing on docker for mac in service mode, using localhost:500/imagename, working on 127.0.0.1:5000/imagename

[subfuzion]

As noted, issues with OS X require using 127.0.0.1 instead of localhost for this to work. Also seeing errors that appear to be related to build service (will discuss with @generalhenry). But otherwise is working, looks good.