LocalShip: added self-signed certificate generation
fixed invokation using `python3 -m dominator.actions`
`dominator shipment generate` can now list available obedients and obedient entrypoints
improve README.md (not all mentioned features are ready yet)
improved commands' docstrings
README.md: added Why Not? section
Merge pull request #51 from nikicat/master

README.md rewrite, various improvements