Move all public *Tools.h in src.

This by definition remove all the tool functions from the public API.

src/search_renderer.cpp

@@ -30,7 +30,7 @@
 
 #include <mustache.hpp>
 #include "kiwixlib-resources.h"
-
+#include "tools/stringTools.h"
 
 namespace kiwix
 {
@@ -155,4 +155,4 @@ std::string SearchRenderer::getHtml()
   return ss.str();
 }
 
-}
+}