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/App/DrawSVGTemplate.cpp

@@ -34,7 +34,6 @@
 #include <Base/Console.h>
 #include <Base/FileInfo.h>
 #include <Base/Quantity.h>
-#include <Base/Tools.h>
 
 #include "DrawPage.h"
 #include "DrawSVGTemplate.h"
@@ -205,7 +204,7 @@ bool DrawSVGTemplate::getTemplateDocument(std::string sourceFile, QDomDocument&
     if (sourceFile.empty()) {
         return false;
     }
-    QFile templateFile(Base::Tools::fromStdString(sourceFile));
+    QFile templateFile(QString::fromStdString(sourceFile));
     if (!templateFile.open(QIODevice::ReadOnly)) {
         Base::Console().Error("DrawSVGTemplate::processTemplate can't read embedded template %s!\n", PageResult.getValue());
         return false;