Support for parallel data modules.

Support for parallel data modules.

Main changes:
 - Add parallelDataStarted() to AnalysisDataModuleInterface to
   initialize modules for parallel processing of data.  If this method
   is called, and the module returns true, then the module accepts that
   frame notification methods can be called in relaxed order: the frames
   can be started in any order, and multiple frames may be active
   simultaneously.
 - Implement this method in the existing modules, either explicitly or
   by using convenience base classes.
 - Add notification methods to AnalysisDataModuleManager to notify
   parallel frames.  These methods are called as soon as the data is
   available to notify those modules that accept parallel data.
   Existing methods were changed to only notify the serial modules.
 - Make AnalysisDataStorage call the new notification methods
   appropriately.  In most cases, this absorbs the complexity that these
   new methods bring.
 - Update (part of) the unit tests to make it possible to test this
   relaxed frame ordering.

Part of #869.

Change-Id: I3cccf78a09221b8181c3d8b217a793c996d0c522