suppress AttributeErrors when exiting "with addcontext()"
removed deprecated make_shipment function
added "ship info" command
shipment generate: print local variables after stacktrace
fixed "task exec"
fixed LocalShip usage with default config
handle "Unable to remove filesystem for .* directory not empty" Docker error
added "volume erase" command
SourceImage: ENTRYPOINT support
YamlFile: disab;e "default flow style" when dumping
Task: use LocalShip as ship by default
Door.paths replaced with Urls (API change)
YamlFile: allow to construct via callable instead of dict
refactored make_backrefs
Container: added "links"
Volume: do not except in __repr__ when there are not backref to container
Bump version: 9.1.0 → 10.0.0
Merge pull request #63 from nikicat/master

Refactoring, new entity Url, added more commands, fixed bugs