Change from EDA_COLOR_T to COLOR4D globally; arbitrary color support

eeschema now supports arbitrary colors for all object types, and
pcbnew does in GAL canvas.  When switching from GAL to legacy canvas,
pcbnew will convert colors to the nearest legacy color.

eeschema/sim/sim_plot_frame.cpp

@@ -561,7 +561,7 @@ void SIM_PLOT_FRAME::updateSignalList()
     {
         wxBitmap bitmap( isize, isize );
         bmDC.SelectObject( bitmap );
-        wxColor tcolor = trace.second->GetTraceColour();
+        wxColour tcolor = trace.second->GetTraceColour();
 
         wxColour bgColor = m_signals->wxWindow::GetBackgroundColour();
         bmDC.SetPen( wxPen( bgColor ) );