store: do not use environs/config

Also make charm.DirSuite use IsolationSuite.
Use the external MgoSuite.

Mostly mechanical.
Remove the testing/mgo* bits which are now in github.com/juju/testing.
Add testing.Certs to be used when registering the MgoSuite tests.
Merge pull request #59 from rogpeppe/007-charm-no-envconfig

store: do not use environs/config

Also make charm.DirSuite use IsolationSuite.
Implemented ListNetworks in dummy provider and stubbed it out in the others
store: use IsolationSuite in ConfigSuite
Merge pull request #58 from dimitern/511-environ-listnetworks-stubs

Introducing Environ.ListNetworks()

Provides a way for juju to discover what networks
are available from the provider. Later, we'll use
that information to discover networks initially
(at bootstrap) and to update them when they change.

Implemented in dummy provider only and stubbed it
out in the others

In a follow-up a concept of "pending networks" will
be introduced in state to hold such networks until
the user decides to use them (i.e. by running
juju add-network --existing).
Add testing package tests, rename getCerts.
Merge pull request #62 from rogpeppe/008-store-configsuite-isolationsuite

store: use IsolationSuite in ConfigSuite

This removes a dependency on github.com/juju/juju/testing.
Merge pull request #61 from frankban/external-mgosuite

Use the external MgoSuite.

Mostly mechanical.
Remove the testing/mgo* bits which are now in github.com/juju/testing.
Add testing.Certs to be used when registering the MgoSuite tests.