Make sure projects are cleaned up nicely when frames close

PROJECT objects will be deleted by SETTINGS_MANAGER::UnloadProject
so we need to make sure that this is called at an early enough point
in the closing process that anything needed by the PROJECT dtor
is still around.

Also fix an issue where the schematic worksheet was depending on
the project existing after the schematic had been reset.

pcbnew/pcb_base_edit_frame.cpp

@@ -22,6 +22,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
  */
 
+#include <kiface_i.h>
 #include <pcb_base_edit_frame.h>
 #include <tool/tool_manager.h>
 #include <pcb_layer_widget.h>
@@ -59,6 +60,10 @@ PCB_BASE_EDIT_FRAME::~PCB_BASE_EDIT_FRAME()
         GFootprintList.WriteCacheToFile( &footprintInfoCache );
     }
 
+    // Close the project if we are standalone, so it gets cleaned up properly
+    if( Kiface().IsSingle() )
+        GetSettingsManager()->UnloadProject( &Prj() );
+
     GetCanvas()->GetView()->Clear();
 }