Utils: Rename FileName to FilePath

More in line with QFileInfo terminonlogy which appears to be
best-of-breed within Qt.

Change-Id: I1d051ff1c8363ebd4ee56376451df45216c4c9ab
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/todo/todoitemsscanner.cpp

@@ -54,7 +54,7 @@ void TodoItemsScanner::processCommentLine(const QString &fileName, const QString
 
     for (int i = 0; i < newItemList.count(); ++i) {
         newItemList[i].line = lineNumber;
-        newItemList[i].file = Utils::FileName::fromString(fileName);
+        newItemList[i].file = Utils::FilePath::fromString(fileName);
     }
 
     outItemList << newItemList;