Missing pattern-matching outputs

[alexcjohnson]

Fixes #1216

Pattern-matching callbacks had some issues with ALL wildcards in their Output, reported by user @jaser on the forum. Everything worked well as long as the ALL matched something, but if it didn't we would throw an error.

There are a number of additional cases to consider, involving various combinations of ALL and MATCH wildcards and multiple outputs, as enumerated in #1216 - I will comment on the tests which of these cases each covers. And as discussed in #1216, we will NOT trigger a callback simply because one or more output items was removed. If you want that to happen, include the output component set as inputs as well - our suggestion is to just change the prop to 'id' to avoid circular dependencies, and as a side benefit you get a clean list of the IDs involved.

• I have run the tests locally and they passed. (refer to testing section in contributing)
• I have added tests, or extended existing tests, to cover any new features or bugs fixed in this PR
• I have added entry in the CHANGELOG.md

[Marc-Andre-Rivet]

Will be honest, not 100% certain I understand all the intricacies of the code change, but the tests seem 👌 -- 💃

[alexcjohnson]

Thanks @Marc-Andre-Rivet - this part of the code probably still is more convoluted than it would need to be, though I was pleased to see that this particular change actually slightly reduced LOC in src. I'm glad you're poking around in it, as we continue updating things I'd appreciate any suggestions you have to further clean it up!