WIP: small bug fixes

- LayoutView should accept technology names that are valid only
- CellView now also sends an "active cellview changed" event when
  loading a layout in "replace layout" mode.

src/laybasic/layCellView.cc

@@ -217,7 +217,11 @@ void
 LayoutHandle::set_tech_name (const std::string &tn)
 {
   if (tn != m_tech_name) {
-    m_tech_name = tn;
+    if (lay::Technologies::instance ()->has_technology (tn)) {
+      m_tech_name = tn;
+    } else {
+      m_tech_name = std::string ();
+    }
     technology_changed_event ();
   }
 }

src/laybasic/layLayoutView.cc

@@ -3124,6 +3124,9 @@ LayoutView::load_layout (const std::string &filename, const db::LoadLayoutOption
   }
   update_content ();
 
+  //  this event may not be generated otherwise:
+  active_cellview_changed (cv_index);
+
   return cv_index;
 }