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/qbsprojectmanager/qbscleanstep.cpp

@@ -170,7 +170,7 @@ void QbsCleanStep::updateState()
 void QbsCleanStep::createTaskAndOutput(ProjectExplorer::Task::TaskType type, const QString &message, const QString &file, int line)
 {
     ProjectExplorer::Task task = ProjectExplorer::Task(type, message,
-                                                       Utils::FileName::fromString(file), line,
+                                                       Utils::FilePath::fromString(file), line,
                                                        ProjectExplorer::Constants::TASK_CATEGORY_COMPILE);
     emit addTask(task, 1);
     emit addOutput(message, OutputFormat::Stdout);