def store(priority, options = nil, &block)
      found = @filters_array.assoc(priority)
      raise KeyError if found.nil?
      found.last.store(options, &block)
    end
def store(priority, options = nil, &block)
      found = @filters_array.assoc(priority)
      raise KeyError if found.nil?
      found.last.store(options, &block)
    end
initializes priorities and coresponding list of filters
 @param priorities [Array|Object] a list of priorities to order filters
 adds a priority filter

 @param priority [Object]   anything that was part of +priorities+ array
 @param options  [Object]   forwarded to Filters.store
 @param block    [Proc]     forwarded to Filters.store
 @raise          [KeyError] when priority not matching priorities is used