adds methods window and where_and

[belchior]

New features

Added window method on Select builder

use sql_query_builder as sql;

let query = sql::Select::new()
  .window("win")
  .as_string();

Added where_and method on Select, Delete and Update Builders

use sql_query_builder as sql;

let select_query = sql::Select::new()
  .from("carts")
  .where_clause("login = $1")
  .where_and("session_id = $2")
  .where_and("created_at >= current_date")
  .as_string();