some improvements to select_query_builder and started insert_query_builder

source/orm/query/select_query_builder.cpp

@@ -64,6 +64,10 @@ void select_query_builder::push(const std::string &column_name) {
   entity_query_data_.columns.emplace_back(&it->second, column_name, build_alias('c', ++column_index));
 }
 
+const select_query_data & select_query_builder::query_data() const {
+  return entity_query_data_;
+}
+
 std::string select_query_builder::build_alias(const char prefix, const unsigned int count) {
   char str[4];
   snprintf(str, 4, "%c%02d", prefix, count);