[dasc] Arrays support reordering of array items

On top of #181 we need to add support for reordering of array items. This is based on customer feedback.

Start by reading issue #181 to understand the existing array support and how the dasc shell represents array items. Trace the related entry point and determine how reordering should be exposed. Done means array items can be reordered without losing their contents or order.

Written by the indexing model from the issue text.