ENH: adding handle to RealTimeClock

Change-Id: I447e4835e66568bd304b34488d2af9b7489dd4e8
BUG: DiffusionTensorReconstruction lacked Progress

The DiffusionTensorReconstructionImageFilter was not reporting progress events.
This commit introduces progress reporting using the ProgressReporter class, and
verifies its proper behavior in the test, with the FilterWatcher class.

Change-Id: I33343267c8439723c41688dbd4168adef2e93265
Merge topic 'timeprobe'

974ec904 ENH: adding handle to RealTimeClock
Merge topic 'DiffusionTensorImageFilterProgressReport'

4f5e993e BUG: DiffusionTensorReconstruction lacked Progress