Allow use of numbered expressions for well pad indexing

[EvanKirshenbaum]

This one is trivial, but I'm adding the issue to have something to refer to in the commit.

Currently, if you want to identify a well, you say

well #1 
well #(n+1)

The syntax is the same for heaters, chillers, extraction points, and magnets.

If you want, on the other hand, to talk about a pad within a well, you say

w[1]
w[n+1]

This is ugly for a couple of reaons:

1. It's a different way to specify the same sort of thing
2. It's not clear that what you get when you index into a well is a well pad.

It would be more consistent to use a hybrid between attribute syntax and numbered item syntax:

w's pad#1
w.pad #1 

possibly with synonyms of internal pad, interior pad, well pad.

Migrated from internal repository. Originally created by @EvanKirshenbaum on Feb 11, 2023 at 5:02 PM PST.