Carbon flow map + status messages

Brand new parallelized flow method that Drew has been writing tests for and flows the carbon as intended, thus this pull resolves issues #5 #124 and #125.  Status object now also holds status messages to be displayed by GUI.  Locks on status object occur during any write operation and when read by the GUI so issue #19 is fixed by this.  Memory management now part of the RiverModel class.  CarbonSource class still needs some doxygen comments but those will be handled in the next week.