Arch BuildingParts now gained a new set of View properties that allows
to define a "capture box". Subsequent Draft and Arch objects, or anything
else that uses Draft.autogroup(), will be automatically added to that
BuildingPart if they are inside the capture box.
Removes unused imports as reported by LGTM.
There are exceptions: `import Arch_rc` is shown as an alert, but has side effects. It's not clear what the best thing to do in those cases is, so I've left them for now.
* The import code will manually set 2x3 attributes
* The import code will rely on "smart" attributes for ifc 4
* ArchSite and ArchBuildingPart now support IFC
* IfcSite lat/lon is left alone until I better understand how coords work
* Properly handle offset2D and arch objects in Draft Stretch
* Allow the WP of Arch BuildingParts to stay weak
* Fixed Draft Edit making Wires not plane anymore
* Dont change the WP if already perpendicular to current view
* Fixed DXF import of Polyfaces
