Propogate template fitting information to agccActor

In order to fit the templates to the PSFs in the AG camera, the agccActor and centroiding routine need

• dZ: the offset in focus compared to the focus in autoguider. This can be calculated from the database if the value of m2_pos3 for a focussed autoguider is known.
• the reference positions of the stars in the focussed image
• the template themselves

The first two items could be obtained from agc_exposure if the agc_exposure_id for the reference image is known.

The third item could be stored in pfs_instdata (and, if necessary, updated in the same way as other calibration files).