common/docker: changed container functions to methods on container struct

-moved Docker.update from orchestrator to common/docker
- changed names of structs in common/docker to Docker, Container, Image
(removed "Info")
common/docker: undid Container methods back to Docker methods

- orchestrator: edits for naming consistency
common/docker: fixed compiler errors
common/docker: re-changed Stop and Delete to methods on Container struct

- need to change image functions to methods on Image struct
- need to update function names/calls in orchestrator/main
common/docker: changed image functions to methods on Image struct

- added Tag field to Image struct, change Tag(...) function name to
AddTag(...)
- fixed naming consistency errors in skeleton/main and orchestrator/main
- need to fix StartState() and StartRepository() functions in
orchestrator/main
Merge branch 'master' into HTTP

Conflicts:
	src/common/docker.go
	src/orchestrator/main.go
	src/skeleton/main.go
Fix merge problems, make everything work again