Add ability to reorder members in a concept set

This is conceptually similar to OCLOMRS-919, but where that ticket applied to concept answers, this applies to concept sets. The solution should be basically the same though.

We need to enable users of the dictionary manager to be able to determine the default order of concepts in a concept set. This is done in OpenMRS by setting the sort_weight property of the ConceptSet object to an appropriate value (1, 2, 3, etc.).

We need to modify the dictionary manager to allow the user to drag and drop concept members into a particular order. This order should be stored in the sort_weight field of the extras object. Where present, this sort_weight should also determine the order that concept set members are displayed in.

This feature has been requested by PIH.