Merge NamedTuple transforms by merging the underlying NamedTuples

[Ickaser]

This may not be strictly necessary, but I have found it convenient to be able to merge multiple NamedTuple transformations by merging the underlying NamedTuples. Previously I did this by relying on the internal fields, but that approach broke (which is totally reasonable, it was an implementation detail).

Should this be a documented feature, in addition to tested?

[devmotion]

Generally it would be good to ensure it's inferred.

[tpapp]

Yes, please mention it in the docs, eg in this sectio.

[Ickaser]

I've added a little note to the docs which suggests the way I am using this; if it should be broadened or not have the link to ConstructionBase.setproperties I am open to suggestions.

[tpapp]

The note in the docs is fine, the documentation is probably due a rewrite one of these days so I will mention this.

[Ickaser]

Is there anything else this needs before being merge-able (haha)?

[tpapp]

Yes, can you please add a trivial test set with collisions (overlapping names)? It is fine to rely on merge, but it something changes I want to be in the position to catch that.

After that, I will merge immediately, I think you address the concerns of @devmotion. Thanks for all the great work!

[Ickaser]

I've added a test for name collisions (and reworded the docs to demonstrate the same thing). Thanks!