The API of `Registry` has been modified as follows:
 - `Registry(name)` returns the registry of the given database
 - `Registry.new(name)` forces the creation of a new `Registry` object
 - `Registry.delete(name)` discards the given registry
 - `Registry.delete_all()` discards all registries
 - `registry.setup_signaling()` initializes the signaling for `registry`
 - `registry.check_signaling()` returns an up-to-date `registry`
 - `registry.signal_registry_change()` notifies that `registry` has changed
 - `registry.signal_caches_change()` notifies potential cache invalidation

- Preserved explicit 3rd-party copyright notices
- Explicit boilerplate should not be necessary - copyright law applies
  automatically in all countries thanks to Berne Convention + WTO rules,
  and a reference to the applicable license is clear enough.

Courtesy of Daniel Reis

Let 2015 be a year without modelines!
cf #4174

Streamed file or interactive console are both available whether or not a
database is specified.

Now I have a machine gun. Ho-ho-ho.

It starts an interactive Python console. If a database is provided, with the
`-d` argument `env` is bound to an Environement with the uid and context of
SUPERUSER_ID and `self` is bound to a RecordSet of the corresponding res.users.

Courtesy of Daniel Reis, reworked to be a bit more agnostic.

Command class is moved from __init__.py to command.py to improve imports of
__init__.py