FR-003: Add a route to GET the pose of an image

[gdozot2]

We should first try to provide a route to GET the pose of an image, e.g.:
https://myInstance.ch/api/images/793/pose
This pose should be served using different conventions for

1. its position (e.g. different projection systems) and
2. its orientation in space (e.g. different ways of expressing the orientation relative to a reference frame
3. eventually geometric errors attached to each of the above values