Build JSON API changes
New 'buildstep_plugins' list
New Plugin :
- docker_api
- reactor_config
Bug Fixes
Parent's environment variables now correctly handle multiple '='
Improvements
New plugin type "BuildStepPlugin" was added,
these plugins are used for actual building of images,
this way we are abstracting the build phase, and make it
configurable via plugins, there is docker_api plugin which
is doing docker image build by default