Geometrical model structure editing

When editing the model structure one can create new groups (model structure tree nodes), delete, cut/copy to the exchange buffer or paste geometrical and structural objects (surfaces, meshes, curves, points and groups) from the exchange buffer.

Predefined groups (Full model, Part, Workpiece, Fixtures, 2D Geometry), and all objects inside 2D Geometry group cannot be deleted or cut into the exchange buffer. However copying the objects into the exchange buffer is possible without any limitations. Objects copied from 2D Geometry will lose their connection with that environment, and if any subsequent changes made in the 2D geometry mode, these objects will remain unaltered.