Docker Studio - action-wide cache of docker state

[mdutoo]

In 0ed0d00 (see #193) I've already explictly cached the list of Docker containers once retrieved, in order to avoid having one docker-machine call per container in startAll and synchronize.

But a better architecture would be to let DockerMachine/ContainerManager to implement interfaces, and to wrap their actual implementation in an implicit request/action-wide cache, in an as much as possible standard (cache JSR) and automated (aspect-like defined, rather than explicitly coded wrapper) way.

Note that it wouldn't improve performance upon 0ed0d00 , which is only twice faster than before, since it still does one "docker start" command per container. The only way to be faster would be to do a single, multi-container "docker start" (if it exists ?).

[cgourdin]

Done with startall command in docker studio v2.