Add support for sorting

[RickMoynihan]

Format needs to define which dimension rows are sorted on and the direction it is sorted in ASC/DESC.

[zeginis]

In some cases lexicographical ordering is not appropriate. E.g. the days of the week should be Monday, Tuesday, Wednesday, Thursday ...

[BillSwirrl]

Yes that sounds a good suggestion. In some of our other work we have added a triple with predicate http://www.w3.org/ns/ui#sortPriority to each concept in a concept scheme, then use that in the PublishMyData user interface to order items in different situations. But I can see some options to return things ready-ordered in the API will be useful - especially if paging the results