Base: Drop QString-std::string conversion functions from Tools

Convenience helpers function Tools::toStdString and Tools::fromStdString
were implemented for Qt4 or older to perform utf8 aware conversion as
QString::toStdString/QString::fromStdString were using toAscii/fromAscii
internally (see https://dreamswork.github.io/qt4/classQString.html).

Since Qt5 QString uses toUtf8/fromUTf8, which makes the helper functions
obsolete (see https://doc.qt.io/qt-5/qstring.html#fromStdString).

src/Mod/TechDraw/Gui/TaskActiveView.cpp

@@ -30,7 +30,6 @@
 
 #include <App/Document.h>
 #include <Base/Console.h>
-#include <Base/Tools.h>
 #include <Gui/Application.h>
 #include <Gui/BitmapFactory.h>
 #include <Gui/Command.h>
@@ -203,7 +202,7 @@ TechDraw::DrawViewImage* TaskActiveView::createActiveView()
                  QImage::Format_RGB32);    //arbitrary initial image size.
     image.fill(QColor(Qt::transparent));
     Grabber3d::quickView(view3d, bg, image);
-    bool success = image.save(Base::Tools::fromStdString(tempName));
+    bool success = image.save(QString::fromStdString(tempName));
 
     if (!success) {
         Base::Console().Error("ActiveView could not save file: %s\n", fileSpec.c_str());