Add dump command

Change-Id: If38d01ebb8788090f91a76daf6b7fc9add0320b7
diff --git a/src/sysrepo_access.hpp b/src/sysrepo_access.hpp
index 3150791..016d49c 100644
--- a/src/sysrepo_access.hpp
+++ b/src/sysrepo_access.hpp
@@ -41,6 +41,7 @@
     void discardChanges() override;
     void copyConfig(const Datastore source, const Datastore destination) override;
 
+    std::string dump(const DataFormat format) const override;
 private:
     std::vector<ListInstance> listInstances(const std::string& path) override;
     [[noreturn]] void reportErrors() const;