?Union of two groups?, ?Union of two groups? and ?Cut of two groups? dialog boxes are updated for supporting works with several groups instead of two groups only
New ?Create group of underlying entities? dialog box is provided. It is intended for creating groups of entities from existing groups of superior dimensions (groups of nodes from group of faces, for example). Dialog contains
1) line edit for defining name of new group,
2) combo-box for defining dimension of elements (nodes, edges, etc),
3) list-box for defining source groups
