Added SceneObject class.  This class is the base class for all "Scene" objects.
Removed geometry type parameter from all scene objects' constructor.  All geom type are set through the setGeomType() function now.
Function name changes.
Added singleton pattern to ColorCoder.
Modified Renderable to derive from SceneObject.  Removed duplicated functions.  Changed some function names.
Added Pickable and Selectable.  Pickable allows an object or its vertices to become pickable.  Selectable stores picked results.
Updated all Renderable objects(Entity, Marker) with SceneObject changes.
Added Pickable objects(PickableGeom, PickableLoc, and PickablePnts).
Removed PickableMarker.
Added Selectable objects(SelectedGeom, SelectedLoc, and SelectedPnt).
Make most VSP windows non-modal.

Non-modal windows stay on top, but allow interaction with other windows.
Make Geom screens non-modal.
Added ruler render object.
Updated VSPenum in Common.  Added ruler and picking object enums.
Updated Scene with all previous changes.
Added ruler and picking properties to DrawObj.
Added Labels to core.  The Labels store data, and later used to generate xml or send to render.
Updated cmake build file for labels.
Added Label GUI to gui_and_draw.
Added screenToWorld and screenToNDC in viewport class.