Attacher: line and point AttachEngines. Other changes.

* propose attachment modes
* refactor setUp and Copy
* split off postprocessing from 3D to reuse in 1D and 0D calculations
* AttachableObject: fix error printout in onChange
* AttachableObject: no more defaults to Attacher3D
* implementation of lines and points attachment (some of the proposed modes).
* refactor getShapeType, add getShapeType(obj, sub); add a flag to eRefType enum, indicating that referenced thing is a whole object that has placement.
* change readLinks to be static, and obtain shape types in the process.
* test mode enums lengths equality
* extend ObjectXY to work on conics.
* Fix upside-down sketches attached as TangentPlane on most shapes.
* Fix crash when a shape of unlisted type is in the links.
* fix attaching to datum lines go crazy because of infinities.
* abs->fabs
* support for App::Line
* Add namespace qualifiers to TYPESYSTEM_SOURCE-like stuff

src/Mod/Part/App/Part2DObject.cpp

@@ -67,6 +67,7 @@ PROPERTY_SOURCE(Part::Part2DObject, Part::AttachableObject)
 
 Part2DObject::Part2DObject()
 {
+    this->setAttacher(new AttachEngine3D);
 }