IDocument: Make mimeType a value member

Change-Id: I2e90ccf0a45ae8d00bcd00ec77fe0d9776f2f119
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/tasklist/taskfile.cpp

@@ -64,11 +64,6 @@ QString TaskFile::suggestedFileName() const
     return QString();
 }
 
-QString TaskFile::mimeType() const
-{
-    return QString();
-}
-
 bool TaskFile::isModified() const
 {
     return false;

src/plugins/tasklist/taskfile.h

@@ -47,7 +47,6 @@ public:
 
     QString defaultPath() const;
     QString suggestedFileName() const;
-    QString mimeType() const;
 
     bool isModified() const;
     bool isSaveAsAllowed() const;