Add functionality to the local dev tools.

[FrenjaminBanklin]

Closes #1932.

• Adds the ability to generate new instructor or learner users on demand.
  • Can optionally provide first/last names.
• Adds the ability to add/remove permissions to users on demand.
• Adds the ability to choose a specific user for the login/picker tools.
• Adds the ability to choose a specific user and module for the preview/view tool.
  • Retains option for enabling score imports.

Apparently the dev tools never had unit tests, so they continue to not have unit tests.

[jpeterson976]

This is awesome, especially the option to add permissions so we don't have to manually update the database to be able to view stats.

Only minor thing I noticed is there are two "add permission" options on the page, though the code for the second one actually removes instead of adds. I also had the idea that being able to remove users might be good, though looking at the endpoints there's not actually anything that does that so it'd probably be more work than it's worth and likely wouldn't get much use anyway.

[FrenjaminBanklin]

Looks like that was a copy/paste fail. Fixed it and pushed.

It might be interesting to see what breaks if users are deleted, but that's currently not expected to ever happen in practice. Like you said, there doesn't appear to be anything anywhere in the code to handle deleting user records - if we wanted to do that, we'd have to remove them from the database by hand regardless of the environment. But since it doesn't seem like it's even possible, I think I'm okay with not having a button for it.

[jpeterson976]

Awesome, LGTM.

I didn't think about all the other repercussions of deleting a user and the cleanup that it would require, so that's definitely not something that's necessary to add.