Add dump command

Change-Id: If38d01ebb8788090f91a76daf6b7fc9add0320b7
diff --git a/src/datastore_access.hpp b/src/datastore_access.hpp
index b159ab3..5a9cdd1 100644
--- a/src/datastore_access.hpp
+++ b/src/datastore_access.hpp
@@ -56,6 +56,7 @@
     virtual void commitChanges() = 0;
     virtual void discardChanges() = 0;
     virtual void copyConfig(const Datastore source, const Datastore destination) = 0;
+    virtual std::string dump(const DataFormat format) const = 0;
 
 private:
     friend class DataQuery;