Merge pull request #385 from jzelinskie/master

Add comment for auth-less mailserver.
Add docs on build support setup
Better formatting
Fix some of the language
Change the image name to make it more clear
Clarify this is a beta and that updating requires pulling a new image
Merge pull request #386 from josephschorr/master

Add docs on enabling build support
enterprise-registry: more info about builds
Merge pull request #388 from robszumski/build-docs

enterprise-registry: more info about builds
enterprise-registry: add buider diagram
Merge pull request #389 from robszumski/build-image

enterprise-registry: add buider diagram
Warn about repo access for build worker repo.