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.h

@@ -23,7 +23,7 @@
 #ifndef VIEWPROVIDERSKETCHBASED_H_QKP3UG9A
 #define VIEWPROVIDERSKETCHBASED_H_QKP3UG9A
 
-#include "ViewProvider.h"
+#include "ViewProviderAddSub.h"
 
 namespace PartDesignGui {
 
@@ -44,6 +44,7 @@ public:
     std::vector<App::DocumentObject*> claimChildren(void)const;
 
     virtual bool onDelete(const std::vector<std::string> &);
+
 };
 
 } /* PartDesignGui  */