Remove pathCache and replace it with syncmap
Cleanup NewBuilder
Create an api/server/backend/build
Extract BuildTagger
Signed-off-by: Daniel Nephin <dnephin@docker.com>
Redefine a better interface for remote context dependency.
Separate Dockerfile build instruction from remote context.
Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
