pixelsampler: added pixel sampler panel

When visible, this panel will show the current reference and display transformed
color under the cursor of any viewer.

app/panel/pixelsampler/pixelsamplerpanel.cpp

@@ -0,0 +1,23 @@
+#include "pixelsamplerpanel.h"
+
+PixelSamplerPanel::PixelSamplerPanel(QWidget *parent) :
+  PanelWidget(parent)
+{
+  // FIXME: This won't work if there's ever more than one of this panel
+  setObjectName("ProjectPanel");
+
+  sampler_widget_ = new ManagedPixelSamplerWidget();
+  setWidget(sampler_widget_);
+
+  Retranslate();
+}
+
+void PixelSamplerPanel::SetValues(const Color &reference, const Color &display)
+{
+  sampler_widget_->SetValues(reference, display);
+}
+
+void PixelSamplerPanel::Retranslate()
+{
+  SetTitle(tr("Pixel Sampler"));
+}