Started work on progress monitor.
Added progress monitor to TimeDependent.
Added unit test for ProgressMonitor.
Refactor ProgressMonitor into ProgressMonitor, ProgressMonitorTime, and ProgressMonitorStep.

Setup progress monitor for TimeDependent and GreensFns problems.
Merge branch 'baagaard/feature-progress-monitor'

* baagaard/feature-progress-monitor:
  Refactor ProgressMonitor into ProgressMonitor, ProgressMonitorTime, and ProgressMonitorStep.
  Added unit test for ProgressMonitor.
  Added progress monitor to TimeDependent.
  Started work on progress monitor.