Separate distributed from single node GraphDb

Summary:
To clean the working directory after this diff you should execute:

```
rm src/database/counters_rpc_messages.capnp
rm src/database/counters_rpc_messages.hpp
rm src/database/serialization.capnp
rm src/database/serialization.hpp
```

Reviewers: teon.banek, msantl

Reviewed By: msantl

Subscribers: pullbot

Differential Revision: https://phabricator.memgraph.io/D1636

tests/concurrent/network_read_hang.cpp

@@ -13,7 +13,7 @@
 #include <gtest/gtest.h>
 
 #include "communication/server.hpp"
-#include "database/graph_db_accessor.hpp"
+#include "database/single_node/graph_db_accessor.hpp"
 
 static constexpr const char interface[] = "127.0.0.1";