Rework needed for LayoutView management

The application got unstable on exit under various conditions
(e.g. LayoutView created in script). Reason was the ownership
management of LayoutView which interfered with Qt widget
lifetime management.

The solution now is based on a clean widget/view hierarchy
and a consistent plugin parent/child relationship.

In addition, a new class is enabled which allows creating
a true QWidget (rather QFrame) for a LayoutView again.

testdata/klayout_main/main.rb

@@ -183,6 +183,14 @@ class KLayoutMain_TestClass < TestBase
 
   end
 
+  def test_11
+
+    # Headless LayoutView (GUI enabled)
+    out = `#{self.klayout_bin} -z -rd input=#{File.join(File.dirname(__FILE__), "test1.gds")} -r #{File.join(File.dirname(__FILE__), "test10.rb")} 2>&1`
+    assert_equal(out, "(0,0;8,8)\n")
+
+  end
+
 end
 
 load("test_epilogue.rb")