Store AG geometry in pfs_insdata repo

AG cameras position on PFI is needed for "shuffle" to find guide stars.  Following the discussions at ICS/PFI+MCS telecon on 3 and 10 July 2020, 4 corner of each sensor is proper.

Hassan, Naoyuki and I talked about the file architecture of this information a while ago, looking the current pfi.yaml and Cobra stuffs. To have commonality with Cobra, we'd like to propose:

• List available AG cameras in pfi.yaml (basically all 6 cameras)
• Store 4 corners in another .yaml file (1 file for all cameras, or 6 files per camera)