state: state no longer depends on params.Status

This PR breaks the dependency between the public `state` api and the `apiserver/params` package. Simply put, when you are working with `Status` and `SetStatus` methods on `state` provided types you now use types defined in the `state` package not the `apiserver`.

The effect on the codebase, especially the tests is profound, many tests in the `state` package no longer import `apiserver/params`.

See also https://lists.ubuntu.com/archives/juju-dev/2014-September/003379.html