Sketcher: improve Z layering in edit mode

Especially when using cross section there was cases where sketcher elements ...
 ... wasn't guaranteed to be visible because hidden by other objects

src/Mod/Show/mTempoVis.py

@@ -455,7 +455,7 @@ class TempoVis(object):
         if enable: # clip plane shall be disabled so new placement can be applied
             self.modify(ClipPlane(doc, 0))
 
-        self.modify(ClipPlane(doc, toggle, pla, 0.02))
+        self.modify(ClipPlane(doc, toggle, pla, 0.001))
         sketch.ViewObject.SectionView = enable if enable is not None else not sketch.ViewObject.SectionView
 
     def activateWorkbench(self, wb_name):

src/Mod/Sketcher/Gui/EditModeCoinManagerParameters.h

@@ -67,8 +67,8 @@ struct DrawingParameters
     /** @name Rendering Heights - virtual height introduced in the scenegraph to determine what is
      * drawn on top of what*/
     //@{
-    const float zEdit = 0.001f;      // Height used by temporal edit curves
-    const float zCross = 0.001f;     // Height used by the Axes
+    const float zEdit = 0.002f;      // Height used by temporal edit curves
+    const float zCross = 0.002f;     // Height used by the Axes
     const float zInfo = 0.004f;      // Height used by the Overlay information layer
     const float zLowLines = 0.005f;  // Height used for bottom rendered lines
     const float zMidLines = 0.006f;  // Height used for in-the-middle rendered lines