Default component group name is misleading

Problem/Motivation

The default group name set in the ComponentMetadata constuctor is currently "All Components" (or the available translation thereof). If a component is assigned to a custom group, it is not a member of the "All Components" group, which is misleading if we list all components by group using the group name as a headline.

Furthermore, it is not currently possible to determine whether a component has a group (or a description) set in its configuration: we always get a string value returned.

Proposed resolution

Leave the group unset, and allowing services retrieving components to decide what to do when a group (or description) is not set,