Add KeyvaDB, Backend, and unit test

modules/ripple_app/node/ripple_KeyvaDBBackendFactory.h

@@ -0,0 +1,27 @@
+//------------------------------------------------------------------------------
+/*
+    Copyright (c) 2011-2013, OpenCoin, Inc.
+*/
+//==============================================================================
+
+#ifndef RIPPLE_KEYVABACKENDFACTORY_H_INCLUDED
+#define RIPPLE_KEYVABACKENDFACTORY_H_INCLUDED
+
+/** Factory to produce KeyvaDB backends for the NodeStore.
+*/
+class KeyvaDBBackendFactory : public NodeStore::BackendFactory
+{
+private:
+    class Backend;
+
+    KeyvaDBBackendFactory ();
+    ~KeyvaDBBackendFactory ();
+
+public:
+    static KeyvaDBBackendFactory& getInstance ();
+
+    String getName () const;
+    NodeStore::Backend* createInstance (StringPairArray const& keyValues);
+};
+
+#endif