PartDesign: New features AdditiveHelix and SubtractiveHelix

These features, based on the code for the Pipe class, allow the user
to simply create a helical sweep within PartDesign workbench.

Sample application is threads, springs, coils, augers, etc.

Also, remove needless requirement for positive cone angle on helixes.

Thanks to @bitacovir for helping with the icons
Thanks to @chennes for review
Thanks to @vosk for review
Thanks to @wwmayer for review

Enforce that links stay within scope for ProfileBased features
This also ensures that the Body itself is not used for creating features within
the body, causing a "Graph not a DAG" error.

src/Mod/PartDesign/Gui/ViewProviderSketchBased.cpp

@@ -72,3 +72,4 @@ bool ViewProviderSketchBased::onDelete(const std::vector<std::string> &s) {
 
     return ViewProvider::onDelete(s);
 }
+