Allow importing existing datasets into squiggle distributions.

[Hazelfire]

In my work on GiveDirectly, I found that it would be useful to import a dataset as a sample set distribution to perform KDE on.

For instance, I want to represent the average household size in my model, and I have a collection of data points from an excel spreadsheet that are the different household sizes in Siaya. I would love to be able to simply import these numbers as a sample set distribution to use in my model. There are two other examples where this would be useful, such as having points for the average transfer size, or the average amount GiveDirectly sends to participants.

One possible implementation path would be to add two features:

• Allow users to create custom bindings from places that are not squiggle. Basically importing js values into squiggle code for usage. This could be useful for many other purposes.
• Create a fromSamples function that simply creates a sample set distribution given an array of samples.

[OAGr]

Would this take anything more than #335 and a fromSamples function?

[Hazelfire]

Not really

[OAGr]

Maybe you could move this to a comment on #335? It's tricky to keep track of tons of issues+discussions.

[Hazelfire]

I think I could finish this entire discussion + #335 by the end of the day, so that might help clean up these discussion xD