ingestImagesDecam.py default changed

Following the implementation of RFC-478, ingestImagesDecam.py (a.k.a. DecamIngestTask) ingests raw images by default instead of instcals. This change means that DecamIngestTask behaves more like IngestTask and other ingestion tasks.

Any code that calls ingestImagesDecam.py with --filetype raw or --filetype instcal behaves the same as before.