Implemented changes from reviews.

- Mostly godoc tautological comments.
- Reorganized imports.
- Moved params from apiserver/leadership to apiserver/params namespace.
- Removed bulk oriented calls from client API as they are not yet needed.
- Annotated errors from making facade calls in the client API.
- Now checking that stubbed-out functions are being called.
- Now checking that service and unit tags are correct.
- Cleaned up error messages.
- Upon starting, the lease manager was not checking existing leases for expiration.
- Giving the lease expiration test slightly more wiggle-room in regards to timing.
- Added TODO in state.go to reflect that leasemanager should eventually be peeled off.
- Added tests to the apiserver layer to test authorizer errors.