[MNT] library global object rename

[stevejpurves]

Towards #230

Summary of Changes

• additional css selectors have been added as thebe- one for each instance of thebelab- selectors
• window.thebelab is a reference to window.thebe
• code in examples and test files .spec.js have been changes to use thebe objects/classes exclusively
• whitespace fixes to some recently touched files
• Additional Housekeeping was carried out in the activate widget docs
  • updated minimal_example.rst this to use the latest built in controls
  • moved the custom activate button to it's own example file

TODO:

• document the change and deprecation cycle
• additional testing

[choldgraf]

@stevejpurves could you give an idea of the major changes that have been made? I was expecting a pure "find/replace", but it seemed like there was also some content that had been added (e.g., the custom activate button). I think for things like "replace thebelab with thebe", it'd be best to just do a single thing in the PR so it's not confusing about what has changed.

Also - perhaps we can allow thebelab to work as well for another deprecation cycle or two? (e.g., make thebelab an alias for thebe?)

[stevejpurves]

@choldgraf thanks for the feedback. I added some comments and details in the PR description including a new TODO

• Sorry there are some content changes in here that could have been done as a PR eslewhere (there are more todo) I made these as I was touching that example. (Basically I wanted to preserve what I was taking out of minimal_example.rst in a new example, and further changes are needed to make the docs consistent but I held off a full pass) I'll unsure more atomic PRs going forward.
• I was planning this to allow for deprecation cycles - as css classes and objects are aliased when they are created - which should do it? I have made some inline comments to make it reasoning around the changes clearer and will do some more testing.
• internal references to the thebe/thebelab objects and all examples have been updated to point people to using thebe

[stevejpurves]

Did some additional local testing and confirmed that setting bootstrap: false in options, and then manually calling thebelab.bootstrap() starts the library successfully and all cells are hooked up to kernels and can be run

[stevejpurves]

planning on bringing this one in
cc @choldgraf

[choldgraf]

Was just gonna ask what needs to happen to move it through 🙂 anything you need help with?

[choldgraf]

@stevejpurves did you implement this elsewhere or something?

[stevejpurves]

over zealous clean up on my part @choldgraf
Restored. I am just getting in other smaller changes before bringing this in.
Will rebase this shortly.

[choldgraf]

This all looks good to me - I guess the main thing is to make sure we haven't missed a thebelab* somewhere in there, but it seems good to me!

I added a couple of non-blocking comments, thanks for this helpful maintenance step!

[choldgraf]

I think this makes sense since thebelab still works - we should do a minor version bump when thebelab is removed though