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.
Not a fan of using an interface in the method signature and then just typecasting it to a concrete implementation.  Also not a fan of having arguments on the method that windows just completely ignores.  It's fine if windows doesn't use them, but then it shouldn't be made to look like it can.  I think we just need different methods for ubuntu and windows.  I'm not entirely sure how to do it, but if we're just going to downcast to the implementation, then having the service interface doesn't actually buy us anything.