WIP: Added windows service package

* moved upstart to service/upstart
* added windows service management package.

The current implementation installs the service as tha user under which juju is currently running. This is done because some installers in windows expect that a real human will run it. The "system" user under which services usually run, does not set a proper user profile as well as other attributes, and that might cause some installers to fail.

The downside of this is that to install a service under a password protected user, you need the password for that user. The password is saved as a secure string decodable only by the juju user. The windows userdata script does save the password inside C:\Juju\Jujud.pass. The Install() method reads the encrypted password in that file and decodes it. It is the used to create the service.
Looking into it.

upstart.Config is used for setting up the mongo upstart script as well as the unit agents. It feels like the service should have a method to install itself instead of letting a second type do this. So upstart.Service should have a config attached to it instead of the other way around.