Homogenize naming of calibration flags

This implements RFC-498 and includes:
   - calib_psfUsed -> calib_psf_used
   - calib_psfCandidate -> calib_psf_candidate
   - calib_astrometryUsed -> calib_astrometry_used

to match the other exsiting flags:
   - calib_photometry_used
   - calib_photometry_reserved

and to match the recently updated documentation in afw/doc/table.dox, in
particular: "if the prefix of a field name represents a conceptual group
of multiple fields, use underscores to join the group name to the group
elements."

python/lsst/meas/algorithms/flaggedSourceSelector.py

@@ -32,7 +32,7 @@
 
 class FlaggedSourceSelectorConfig(BaseSourceSelectorTask.ConfigClass):
     field = lsst.pex.config.Field(
-        dtype=str, default="calib_psfUsed",
+        dtype=str, default="calib_psf_used",
         doc="Name of a flag field that is True for Sources that should be used.",
     )
 

tests/test_flaggedSourceSelector.py

@@ -41,7 +41,7 @@ def addGoodSource(src, num=0):
     record['slot_Centroid_y'] = 20. + num
     record['slot_ApFlux_flux'] = 100. + num
     record['slot_ApFlux_fluxErr'] = 1.
-    record.set("calib_psfUsed", True)
+    record.set("calib_psf_used", True)
 
 
 class TestFlaggedSourceSelector(lsst.utils.tests.TestCase):
@@ -50,7 +50,7 @@ def setUp(self):
         schema = lsst.meas.base.tests.TestDataset.makeMinimalSchema()
         schema.addField("slot_ApFlux_flux", type=float)
         schema.addField("slot_ApFlux_fluxErr", type=float)
-        schema.addField("calib_psfUsed", type="Flag")
+        schema.addField("calib_psf_used", type="Flag")
 
         self.src = afwTable.SourceCatalog(schema)
         self.sourceSelector = sourceSelector.sourceSelectorRegistry['flagged']()
@@ -72,7 +72,7 @@ def testSelectSourcesBad(self):
         that our output array is indeed empty.
         """
         addGoodSource(self.src, 1)
-        self.src[0].set('calib_psfUsed', False)
+        self.src[0].set('calib_psf_used', False)
         result = self.sourceSelector.run(self.src)
         self.assertNotIn(self.src['id'][0], result.sourceCat['id'])