Rename CmdlineTask's entry method runDataDef

Prepare Tasks for Gen3 PipelineTask conversion by:
* Renaming CmdlineTask's entry method to `runDataRef`.  The default
  CmdlineTask.TaskRunner now calls a Task's `runDataRef` method on the
  parsed command line inputs.
  `runDataRef` method can take any Gen2 Butler data products.
* Renaming CmdlineTasks previous core methods (e.g. assemble,
  characterize) to `run` when they exist.

python/lsst/meas/base/forcedPhotImage.py

@@ -86,8 +86,8 @@ class ForcedPhotImageTask(lsst.pipe.base.CmdLineTask):
     """!A base class for command-line forced measurement drivers.
 
     This is a an abstract class, which is the common ancestor for ForcedPhotCcdTask
-    and ForcedPhotCoaddTask.  It provides the run() method that does most of the
-    work, while delegating a few customization tasks to other methods that are
+    and ForcedPhotCoaddTask.  It provides the runDataRef() method that does most of
+    the work, while delegating a few customization tasks to other methods that are
     overridden by subclasses.
 
     This task is not directly usable as a CmdLineTask; subclasses must:
@@ -120,7 +120,7 @@ def __init__(self, butler=None, refSchema=None, **kwds):
             self.makeSubtask("applyApCorr", schema=self.measurement.schema)
         self.makeSubtask('catalogCalculation', schema=self.measurement.schema)
 
-    def run(self, dataRef, psfCache=None):
+    def runDataRef(self, dataRef, psfCache=None):
         """!Measure a single exposure using forced detection for a reference catalog.
 
         @param[in]  dataRef   An lsst.daf.persistence.ButlerDataRef. It is passed to the