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/QGITile.cpp

@@ -30,7 +30,6 @@
 #include <Base/FileInfo.h>
 #include <Base/Parameter.h>
 #include <Base/Stream.h>
-#include <Base/Tools.h>
 
 #include <Mod/TechDraw/App/DrawTileWeld.h>
 
@@ -262,7 +261,7 @@ void QGITile::setFont(QFont f, double fSizePx)
 
 void QGITile::setFont(std::string fName, double fSizePx)
 {
-    QString qFName = Base::Tools::fromStdString(fName);
+    QString qFName = QString::fromStdString(fName);
     QFont f(qFName);
     setFont(f, fSizePx);
 }