and various DIALOG classes called from top frames.  See comments in
   {eeschema,pcbnew}/invoke_a_dialog.h.
*) Move some dialog classes into *.cpp files from *.h files.
*) void SCH_EDIT_FRAME::OnErc( wxCommandEvent& event ) was opening the modeless
   ERC dialog more than once if icon was clicked more than once.
*) Remove BOM stuff.