This ticket is part of the implementation of RFC-857, reducing the amount of extra processing that is happening in a default configuration of characterizeImage.
1. Restrict plugins used in characterize to only a minimal list that is either required or is our recommended algorithm (e.g. shape HSM over SdssShape).
2. Default measurePsf to psfex instead of piff, and ensure piff is used where it is needed (possibly just FinalizeCharacterizeTask, which already defaults to piff).
3. Default to psfIterations=1.
4. Cleanup ap_pipe's characterizeImage plugin list/configs to reflect that the default plugins are now appropriate for AP (this should remove the additions that were made on