Align STLs to z=0 when autoplating.

plater.py

@@ -89,6 +89,7 @@ class showstl(wx.Window):
         newrow = 0
         max = [0,0]
         for i in self.models:
+            self.models[i].offsets[2]=-1.0*min(m.facetsminz)[0]
             x = abs(self.models[i].dims[0] - self.models[i].dims[1])
             y = abs(self.models[i].dims[2] - self.models[i].dims[3])
             centre = [x/2, y/2]
@@ -116,7 +117,6 @@ class showstl(wx.Window):
         for i in self.models:
             self.models[i].offsets[0] += centreoffset[0]
             self.models[i].offsets[1] += centreoffset[1]
-          
         self.Refresh()
         
     def right(self,event):