[REVIEW] Initial version of devel images with BlazingSQL added

[rlratzel]

This also include the "Welcome to BlazingSQL" notebook repo and updates to /test.sh to run the welcome NB.

Note: There are other NBs in the Welcome repo, but those are not being run since they require additional dependencies. When the runtime images are using the updated RAPIDS meta-packages (specifically an updated notebook deps package), this can be revisited if it's decided the additional dependencies for the extra Blazing NBs are to be included.

@ajschmidt8 - I left the "clean" option in the updated generate script if you ever find that useful. I can remove that if you don't want that code in there.

[ajschmidt8]

The BlazingSQL stuff looks good.

Regarding generate_dockerfiles.py:
From our chat on Slack, I'm fine with removing the clean flag for initialize_output_dir. I probably shouldn't have had that functionality in there in the first place.

Since the only way to use that flag is to manually edit generate_dockerfiles.py, I think it's probably best to remove it. This way people aren't encouraged to edit that script. It'll also remove some lines of code which is always good.

[ajschmidt8]

nice. approved. just left one minor suggestion to clean up some comments.

[mike-wendt]

This does not create a new image, it changes the core of the devel images. The request made was for a new image that starts with FROM rapidsai/rapidsai-dev or the nightly version. Pushing this to v0.16 until there is a separate image.

[rlratzel]

@mike-wendt there's a long internal email thread that ended with "let’s get the devel containers good to go while we work on improving the conda packaging situation", which I interpreted to be what's in this PR. I didn't realize the original request was still what we wanted after that. I can make the change you're asking for, but like you said, it'll now have to wait for 0.16.

[datametrician]

Let's ask clarifying questions more, and get sign off. This mistake only cost BlazingSQL a few dozen thousand downloads :(

[rlratzel]

Let's ask clarifying questions more, and get sign off.

Agreed. Unfortunately, clarification and sign off was the intent of the PR :( but we'll figure out a different way.

[ajschmidt8]

closing this in favor of #179