rose config-edit: numbered (indexed) array widget to support Fortran array compression syntax

[benfitzpatrick]

It may be useful to have another array widget with better indication of indices of elements.

We have another requirement to have an array widget that can support the namelist array compression syntax, together with index indication to help users keep track. That looks like a variation on this theme - I'll alter the issue title to make it clearer.

[aosprey]

One of my colleagues was recently asking about a feature like this! I think it would be really useful for long arrays.

[benfitzpatrick]

I think we've had 3 users asking for this now, so I'll bump up the priority