Introduce Database.schema()

Author: haikalpribadi

protobuf/database.proto

@@ -47,6 +47,15 @@ message Database {
         }
     }
 
+    message Schema {
+        message Req {
+            string name = 1;
+        }
+        message Res {
+            string schema = 1;
+        }
+    }
+
     message Delete {
         message Req {
             string name = 1;

protobuf/grakn.proto

@@ -31,6 +31,7 @@ service Grakn {
     rpc database_contains (Database.Contains.Req) returns (Database.Contains.Res);
     rpc database_create (Database.Create.Req) returns (Database.Create.Res);
     rpc database_all (Database.All.Req) returns (Database.All.Res);
+    rpc database_schema (Database.Schema.Req) returns (Database.Schema.Res);
     rpc database_delete (Database.Delete.Req) returns (Database.Delete.Res);
 
     rpc session_open (Session.Open.Req) returns (Session.Open.Res);