Add a sort option.

[Dimibe]

Is:

Currently the passed elements need to be sorted in order to assure that the grouping works as expected.

Should:

The list should be sorted before displaying. Make the sorting configurable through a parameter for performance reason. E.g. if the elements are provided by a query ordering the query result should be preferred.

• Name of the option should be sort.
• The option should be optional.
• By default the option should be set to true.