Make IDocument::fileName a member with setter.

Instead of requiring subclasses to implement a method.
Also renames IDocument::rename to IDocument::setFileName,
since it doesn't really rename any files or such.

Change-Id: I1344025c24d2f74a6a983e04fb0a5245f1f37aad
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/qbsprojectmanager/qbsprojectfile.cpp

@@ -36,9 +36,10 @@ namespace QbsProjectManager {
 namespace Internal {
 
 QbsProjectFile::QbsProjectFile(QbsProject *parent, QString fileName) : Core::IDocument(parent),
-    m_project(parent),
-    m_fileName(fileName)
-{ }
+    m_project(parent)
+{
+    setFileName(fileName);
+}
 
 QbsProjectFile::~QbsProjectFile()
 { }
@@ -48,11 +49,6 @@ bool QbsProjectFile::save(QString *, const QString &, bool)
     return false;
 }
 
-QString QbsProjectFile::fileName() const
-{
-    return m_fileName;
-}
-
 bool QbsProjectFile::isReadOnly() const
 {
     return true;
@@ -100,13 +96,6 @@ bool QbsProjectFile::reload(QString *errorString, ReloadFlag flag, ChangeType ty
     return true;
 }
 
-void QbsProjectFile::rename(const QString &newName)
-{
-    // Can't happen
-    Q_UNUSED(newName);
-    Q_ASSERT(false);
-}
-
 } // namespace Internal
 } // namespace QbsProjectManager