Added named pipes support

This branch replaces unix sockets with named pipes on windows.
wip
environs/config: introduce config.UUID()

Introduce `config.UUID()` method to access the uuid of the environment.

A uuid is the canonical indentifier for an environment, and superceeds the environment's name.

For backwards compatability, `config.UUID()` is currently permitted to return "", but once all environments are converted to have an environment uuid in place, this method will change to return a valid uuid for a valid config.
Merge branch 'master' of https://github.com/juju/juju into 150-environs-config-grow-a-uuid-method
Permit uuid to be set if unset, otherwise refuse to set it.
Merge branch 'master' of https://github.com/juju/juju into 150-environs-config-grow-a-uuid-method
Merge branch 'master' of https://github.com/juju/juju into 150-environs-config-grow-a-uuid-method
Merge pull request #302 from gabriel-samfira/named-pipes

Added named pipes support

This branch replaces unix sockets with named pipes on windows.

The "sockets" package name is temporary. It should be named something else that denotes that it will only dial either unix sockets or named pipes. Dialing TCP sockets works the same on both windows and linux.
environs/configstore: make Default a variable
Merge pull request #397 from rogpeppe/013-configstore-default

environs/configstore: make Default a variable

It's useful for testing purposes.
Merge branch 'master' of https://github.com/juju/juju into 150-environs-config-grow-a-uuid-method
responding to review feedback
added env uuid to the state object
Merge pull request #378 from davecheney/150-environs-config-grow-a-uuid-method

environs/config: introduce config.UUID()

Introduce `config.UUID()` method to access the uuid of the environment.
    
A uuid is the canonical identifier for an environment, and superceeds the environment's name.
    
For backwards comparability, `config.UUID()` is currently permitted to return "", but once all environments are converted to have an environment uuid in place, this method will change to return a valid uuid for a valid config.
envUUID on the state should be an environ tag
wip
keep the environ tag as a tag in our getter
wup
Merge pull request #401 from mattyw/add-uuid-to-state

added env uuid to the state object

Add the environment uuid to the state so that we can pass it on to AddEnvUser in a future pr
wip