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/qbsprojectmanager/qbsprojectfile.cpp

@@ -38,7 +38,7 @@ namespace Internal {
 QbsProjectFile::QbsProjectFile(QbsProject *parent, QString fileName) : Core::IDocument(parent),
     m_project(parent)
 {
-    setFileName(fileName);
+    setFilePath(fileName);
 }
 
 QbsProjectFile::~QbsProjectFile()