Read element data

Read type, layer and requested values of the given elements. properties takes addresses: a property ('Group/Name', a built-in name or a property GUID, as search_definitions gives it); 'classification:' (the item ID); 'gdl:' (a GDL parameter of an object, lamp, door, window or other library part element); 'marker:' (a door's or window's marker parameter, Tapir 1.7.1); 'ifc:.' (an IFC property). Lengths in metres, angles in radians, attribute-typed GDL parameters as attribute indexes. 'gdl:', 'marker:', 'ifc:' and 'classification:' read every value, with display names in 'labels'; at most 20 elements per wildcard call. A kind that cannot be read for an element is named in its 'unreadable'. include_classifications adds every system's item GUID.