add missing sql execute statements in connection

include/matador/sql/connection.hpp

@@ -13,9 +13,15 @@ class connection
 {
 public:
   connection();
+  query_create_intermediate create();
+  query_drop_intermediate drop();
   query_select_intermediate select(std::initializer_list<std::string> column_names);
+  query_insert_intermediate insert();
+  query_update_intermediate update(const std::string &table);
+  query_delete_intermediate remove();
 
-  result execute(const std::string &sql);
+  result fetch(const std::string &sql);
+  std::pair<size_t, std::string> execute(const std::string &sql);
 
 private:
   dialect dialect_;