Add HeatSetNuts from Aliexpress and allow nut size to have more than 3 parts

[kcleung]

As per @gumyr request, I am breaking up the pull request #25 from @infused-kim.

Here is the first part of his pull request. Once this PR is done, I will process the balance of the PR #25

1. HeatSetNuts from AliExpress
   They can be purchased here: https://www.aliexpress.com/item/1005005220632314.html

It seems like there are multiple stores / brands that sell the same nuts (same dimensions and images). I picked this one, because he has the largest selection, a large amount of sales and was fast to respond in the support chat.

You can also find the spreadsheet I used to edit the data here:
https://docs.google.com/spreadsheets/d/1ZpZ6ltspaA5y2Nw6DH-3abuv4ToLoAWX3zQu_ON2lfs/edit?gid=0#gid=0

2. Allow nut size to have more than 3 parts
   Some of the AE nuts had the same size thread size and height, but different variations in the outer diameter, such as M2-0.4-H2-D3.2 and M2-0.4-H2-D3.5 (outer diameter 3.2 vs 3.5).

So, I added another - to distinguish between them.

But then the code stopped populating length_size:

if len(size_parts) == 3: self.length_size = size_parts[2]

So, I changed it to allow more than 3 parts.