Close database without asking when unmodified.

Don't ask for confirmation when closing/locking a database and
- it's in edit entry mode
- there haven't been any modifications

Refs #511

src/gui/DatabaseWidget.h

@@ -74,6 +74,7 @@ public:
     QStringList customEntryAttributes() const;
     bool isGroupSelected() const;
     bool isInEditMode() const;
+    bool isEditWidgetModified() const;
     QList<int> splitterSizes() const;
     void setSplitterSizes(const QList<int>& sizes);
     QList<int> entryHeaderViewSizes() const;