Memleak Fixes

Three classes of leaks have been detected and corrected.

1. NetCDF attributes. These are the attribute objects themself for each Grid or Radial.  These are now deleted in the destructors.
2. NetCDF attribute values. Allocated by the NetCDF library - expected to be deleted by user. Helper functions to extract these values, copy to destirnation and delete necessary pointers.
3. NetCDF edges. Allocated by the NetCDF library - expected to be deleted by user. Solved by making a 'array_smart_ptr' template to automatically delete the edges array when the object goes out of scope.

Also....removed a bunch of commented and unused code from wxcavset.