Implemented histogram number of buckets on the Overlay and Map Setting's...

Implemented histogram number of buckets on the Overlay and Map Setting's Dialog's Palette tab.  The number of histogram buckets is a property of the file and also of each map.  When the Palette Normalization is 'Selected Map', the number of buckets is the number of buckets associated with the map.  When the Palette Normalization mode is 'All Maps', the number of buckets property is that associated with the file.