Rename IDocument::fileName --> filePath

That is what it actually is, wrt how Qt API calls it.

Change-Id: Ied02055debf6aad75556b0d9d22e8ba2f72be555
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/qmlprojectmanager/qmlprojectfile.cpp

@@ -41,7 +41,7 @@ QmlProjectFile::QmlProjectFile(QmlProject *parent, QString fileName)
 {
     QTC_CHECK(m_project);
     QTC_CHECK(!fileName.isEmpty());
-    setFileName(fileName);
+    setFilePath(fileName);
 }
 
 QmlProjectFile::~QmlProjectFile()