- track previous time index and to avoid recalculating averages.
- make sure averages are up-to-date before calling write

- added end() method to functionObject, functionObjectList & associated classes
- moved outputFilters from src/sampling -> src/OpenFOAM/db/functionObjects

- this (now deprecated) idiom:
      for (runTime++; !runTime.end(); runTime++) { ... }
  has a few problems:
    * stop-on-next-write will be off-by-one (ie, doesn't work)
    * function objects are not executed on exit with runTime.end()
  Fixing these problems is not really possible.

- this idiom
      while (runTime.run())
      {
          runTime++;
          ...
      }
  works without the above problems.

- can call start()/execute() manually regardless of the execution status

- added clear() method to functionObjectList. It also gets called by ~Time().
  This should destroy function objects before anything else gets
  destroyed (eg, objectRegistry).

- make functionObjectList mutable so it can change behind our back

- added class OSHA1stream for a stream-based calculation method
- dictionary gets digest() method
- dictionaryEntry tweak: avoid trailing space after dictionary keyword