provide default implementation of IFile::reloadBehavior()

there only two classes of files anyway: regularly editable ones which may
ask for interaction, and "background" files which always operate silently.
the regular case is the more complex one, so put that into the base class.

src/plugins/designer/formwindowfile.h

@@ -58,7 +58,6 @@ public:
     virtual bool isModified() const;
     virtual bool isReadOnly() const;
     virtual bool isSaveAsAllowed() const;
-    ReloadBehavior reloadBehavior(ChangeTrigger state, ChangeType type) const;
     bool reload(QString *errorString, ReloadFlag flag, ChangeType type);
     virtual QString defaultPath() const;
     virtual QString suggestedFileName() const;