Document new container release policy

Instead of tagging containers as fresh and stable, we would like to automatically build development and release tags that are automatically built weekly from the packages available in the minefield and release Yum repositories, respectively. Each of these should also have timestamp tags.

For the WN clients, we should also build development and release tags for each OS supported in the latest release series (each with timestamp tags).

Additionally, we should note that changes to the containers themselves may have specific one-off tags (e.g. SOFTWARE-1234.fix-broken-doodad) and how developers should be creating and pushing these tags (manually?).