Fixed crash when browser window graphics region was clicked prior to loading any data.
Updated help files.
For metric surface node coloring, replaced usage of getDescriptiveStatistics() with getFastStatistics().
Removed some that was commented out and previously made function calls with DescriptiveStatistics.
Removed MapSettingsPaletteColorMappingWidget::getDescriptiveStatisticsForHistogram() as it is never called.  It probably was used prior to adding virtual method getMapHistogram() to CaretMappableDataFile.
Continued removing unsused code related to DescriptiveStatistics.  Long ago, most usage of DescriptiveStatistics was FastStatistics.
Removed getMapStatistics() methods that returned DescriptiveStatistics pointer from CaretMappableDataFile and its sub-classes.
Fixed a performance issue CIFTI Files.  Both the Histogram was and FastStatistics were updated every time they were requested, even though the data had not changed.  Logic has been changed to avoid updates of Histogram and FastStatistics and to invalidate them when the data changes.  This also required adding a separate Histogram for the 'limited values' calculation.
Corrections for updating limited values histogram and for when CIFTI matrix file does not have data loaded.
Make 'MapContent' private to CiftiMappableDataFile.  This and other changes are being made in prepartion for WB-396 in which some CIFTI files will have statistics and histogram calculated on all data in the file instead of each map.
Resolve part of WB-396: For parcellated data type files, compute both Histogram and Statistics on all data in the file instead of the selected or single-map data.
Fixed crash that occurred when one tried to copy the loaded row (Overlay ToolBox->Connectivity) from a Dense Connectome File that was on the network.
Related to WB-436: Added a new DataFileException constructor that accepts both the name of the file and the error message in separate parameters.  It then formats the exception message as name of file, a newline, path of file, a new line, and then the exeption message.  When a file with a long path failed read, the message was often to long to display in an error message dialog making it hard for the user to know which file had a problem.
Added validation of CIFTI Mapping Types to verify that those read from the file match the mapping types for the data file type.
Add type of histogram and status (all data in file or per map) to '-file-information' command for CIFTI files.