Make IsrTask a valid CmdLineTask.

The IsrTask was not usable as a CmdLineTask, as it was written to be
called as a subtask of ProcessCcdTask.  This allows the default
IsrTask to be retargeted to camera-specific versions of the ISR
processing.  A new IsrWrapperTask now exists to hold IsrTask for
retargetting in standalone processing, and both processCcd.py and
runIsr.py now read from the same configuration files for each obs_
package.  This has involved migrating configuration values from
config/processCcd.py to config/isr.py for many obs_ packages.

config/isr.py

@@ -0,0 +1,5 @@
+"""
+LSST Sim-specific overrides for IsrTask
+"""
+config.doFlat = False
+

config/isrWrap.py

@@ -0,0 +1,12 @@
+"""
+LSST Sim-specific overrides for IsrWrapperTask
+"""
+import os.path
+
+from lsst.utils import getPackageDir
+from lsst.obs.lsstSim.lsstSimIsrTask import LsstSimIsrTask
+
+obsConfigDir = os.path.join(getPackageDir("obs_lsstSim"), "config")
+
+config.isr.retarget(LsstSimIsrTask)
+config.isr.load(os.path.join(obsConfigDir, "isr.py"))

config/processCcd.py

@@ -1,9 +1,16 @@
-"""lsstSim-specific overrides for the processCcd task
 """
-from __future__ import print_function
+LSST Sim-specific overrides for the ProcessCcdTask
+"""
+import os.path
+
+from lsst.utils import getPackageDir
 from lsst.obs.lsstSim import LsstSimIsrTask
 
+obsConfigDir = os.path.join(getPackageDir("obs_lsstSim"), "config"))
+
 config.isr.retarget(LsstSimIsrTask)
+config.isr.load(os.path.join(obsConfigDir, "isr.py")
+
 # this was the default prior to DM-11521.  New default is 2000.
 config.calibrate.deblend.maxFootprintSize=0