def add_column(col_id, filter_type, options = {})
      columns << FilterColumn.new(col_id, filter_type, options)
      columns.last
    end
Adds a filter column. This is the recommended way to create and manage filter columns for your autofilter.
In addition to the require id and type parameters, options will be passed to the filter column during instantiation.
@param [String] col_id Zero-based index indicating the AutoFilter column to which this filter information applies.
@param [Symbol] filter_type A symbol representing one of the supported filter types.
@param [Hash] options a hash of options to pass into the generated filter
@return [FilterColumn]