Implement/improve mesh assignment/copying

One mesh can now be assigned to another using .assign(), even between different topology kernels. This required proper copying/moving of properties, and re-using old properties that may be referenced elsewhere (e.g. NormalAttrib).

This is mainly intended for Mesh conversion.

src/OpenVolumeMesh/Core/BaseProperty.cc

@@ -32,18 +32,11 @@
  *                                                                           *
 \*===========================================================================*/
 
-/*===========================================================================*\
- *                                                                           *
- *   $Revision: 36 $                                                         *
- *   $Date: 2012-01-10 18:00:06 +0100 (Di, 10 Jan 2012) $                    *
- *   $LastChangedBy: kremer $                                                *
- *                                                                           *
-\*===========================================================================*/
-
 #include "BaseProperty.hh"
 
-#include "ResourceManager.hh"
-
 namespace OpenVolumeMesh {
 
+// define this here to emit a vtable only in this translation unit
+BaseProperty::~BaseProperty() = default;
+
 } // Namespace OpenVolumeMesh