Refactor container structure and add support for more run arguments

Instead of a tree, containers now need to be listed. This makes it
possible to use Crane with --volumes-from etc. This change also
introduces two new flags. --vverbose will print even more output
then --verbose. --force makes it easier to do several steps in one
go, such as stopping containers before removing them, or recreating
containers without removing them first. Additionally, Crane will not
print errors anymore if you try to stop a container which is not
running anyway.
Update readme to reflect recent changes