Add panel

The side panel opens with the Space key, this panel can contain
    widgets to assist the capture with more features.
    This commit fixes the preview of the tool hiding it when the
    mouse hovers a widget. This is more needed now having a new widget
    inside the CaptureWidget.

src/tools/save/savetool.cpp

@@ -48,7 +48,6 @@ CaptureTool* SaveTool::copy(QObject *parent) {
 }
 
 void SaveTool::pressed(const CaptureContext &context) {
-    // TODO blocks type and others
     if (context.savePath.isEmpty()) {
         emit requestAction(REQ_HIDE_GUI);
         bool ok = ScreenshotSaver().saveToFilesystemGUI(