fixed bug #556 - Premature loading of modules

The Draft and Arch modules now load heavy modules such
as Part or Sketch only when they use them, not anymore
at Init time.

src/Mod/Arch/ArchStructure.py

@@ -21,8 +21,8 @@
 #*                                                                         *
 #***************************************************************************
 
-import FreeCAD,FreeCADGui,Part,Draft,ArchComponent
-from draftlibs import fcgeo,fcvec
+import FreeCAD,FreeCADGui,Draft,ArchComponent
+from draftlibs import fcvec
 from FreeCAD import Vector
 from PyQt4 import QtCore
 
@@ -94,6 +94,8 @@ class _Structure(ArchComponent.Component):
             self.createGeometry(obj)
 
     def createGeometry(self,obj):
+        import Part
+        from draftlibs import fcgeo
         # getting default values
         height = normal = None
         if obj.Length: