add and remove elements from group is imposible

add and remove elements from group is imposible: * some easy and yet significant improvement in the group: entity = element/group - We can't add an entity to an entire group. If we select both and hit the ctrl/g, it will create an unwanted new group and add all entities to that. Perhaps an option should exist that allows the user to drag entities into an entire group, causing the bundle box of the group to expand and wrap around the entity(s). By dropping them, the entities will be added to that group without creating a new group. - We...