This ticket is for implementing changes in obs_decam in order to run processCcd with raw DECam data.

Changes are mostly in DecamMapper and a new class DecamIsrTask is added. A test to retrieve defects with Butler is also added. (testdata_decam is at lsst-dev /lsst8/testdata_decam/ )

The pixels with bit 1 (bad, hot/dead pixel/column) from the Community Pipeline Bad Pixel Masks are used as bad pixels. The CP BPM fits files are directly used as defect files. Due to their large size, they probably should not go into obs_decam repository so they are treated similarly as other calibration products.

With the changes of this ticket, the following ingest defects files into calibRegistry:

ingestCalibs.py . --calibType defect path-to-bpm/*fits

and the following should run past ISR:

processCcd.py .  --config isr.doFringe=False isr.assembleCcd.setGain=False calibrate.doPhotoCal=False calibrate.doAstrometry=False calibrate.measurePsf.starSelector.name="secondMoment"

Running fringe correction with DECam raw data will be in future tickets (DM-4223 and possibly more). Also this ticket does not cover implementing or porting new ISR functionalities that haven't yet been included in ip_isr (such as crosstalk).