Fix bug that caused cf.Field.del_file_location to fail when updating its metdata constructs

[davidhassell]

Fixes #707

Also improves method order in API docs.

[sadielbartholomew]

I've raised one question and one minor suggestion, but this solves the issue at hand and adds new relevant testing so all good and I am happy for this to be merged once those have been considered. Thanks.

[sadielbartholomew]

What (rough) ordering rules are we going for with respect to the API reference listings, e.g. here, for future reference (so I know what to try to abide by when adding new items myself, etc.)? It seemed to be alphabetical before but it appears that you are now preferring some loose form of categorisation based on the form of functionality?

[davidhassell]

Hi Sadie - anarchy rules! Sometimes it seems that alphabetical makes sense, other times some logical grouping seems appropriate. When (no if!) we refactor the whole documentation we'll look at this in the round.

[sadielbartholomew]

anarchy rules

I have that on a T-shirt, with an exclamation at the front (not really, but it would work 😄 )!

Fair enough (when AI takes over it won't be able to automate such rules, so good thinking 😁 ). In that case, I'll generally not touch anything myself as to change the order (not that I had plans to, this would only be when otherwise touching the API reference method or class listings) unless it looks obviously out of alphabetical or (some) grouping order. Thanks for clarifying.