finish and replace on ClassDescriptor aren't currently used in ToClassDescriptor

[tjcrowder]

ClassDescriptor has finish and replace properties, but ToClassDescriptor doesn't do anything with those properties.

I think where we came to in #182 and which was implemented in #199 would make finish and replace on ClassDescriptor obsolete. But I could be mistaken

I think we need to either:

1. Remove them from ClassDescriptor, or
2. Modify ToClassDescriptor to have it look for finish and replace properties and, if either exists, add appropriate type="hook" element(s) to a shallow copy of elementsObject just prior to calling ToElementDescriptors.

(1) is the simple solution; if you want hooks, add them to the elements array. (2) is more concise to use.

FWIW: The direction I lean varies by the minute. On the one hand, KISS. On the other hand, it's pretty simple to say "putting a finish/replace function on the class descriptor effectively adds a type="hook" element with a finish/replace function to elements".

Happy to add it to my PR queue once a decision is made.

[nicolo-ribaudo]

👍 for option 1

[littledan]

Let's read the properties and throw if they are present, and remove them from ClassDescriptor as you say. Option 2 is a bit redundant, as you explained.