code: function getDatabase(index, opts) {
    var db;
    if(!this._databases[index]) {
      db = new Database(this, opts);
      this._databases[index] = db;
    }
    return this._databases[index];
  }
docs: Get a database and inject it into the list at the
  specified index if no db exists at that index.
  
  @param index The database index.
  @param opts Database options.