Add setManifest command to API

[awagner-mainz]

Using Tify as Image Viewer in the context of a digital scholarly edition, I have an issue when dealing with multivolume works. From any position in the work, I want to be able to open the viewer and have it display the corresponding page image.

For monographs, I am (successfully) using the API's setPage command. But for multivolume works - the iiif manifest of which uses a collection with several manifest members - I would eventually need to run something like a setManifest command first.

As I understand, the API does not yet provide such a command. (Changing the manifest/volume manually works.) Can it be implemented?