ResolvedTransformer::Ptr -> ResolvedTransformerPtr

Also introduce ResolvedTransformerConstPtr for consistency and use
it where appropriate.

Change-Id: I4922c71a681e970e57502269d8ee259dcacde39f
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>
Transformer.explicitlyDependsOn added

Change-Id: If4f695878087f0cd72d85e497d918c4f70e42001
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>