Explore turning strict on for Typescript

[NicMcPhee]

If you set strict = true in tsconfig.js, all kinds of red pops up, a lot of which has to do with the possibility that various things could be null or undefined, but we don't handle that gracefully (or at all). In many cases this is the result poor to nonexistent error handling. In other cases, however, it's just complicated because we "know" (because of how Angular works) that something will have a value, but TS can't figure that out.

I feel like we should at least make a significant effort to fix this, but it's definitely not happening now with this lab having to go out in a day or so. Maybe it's something I look at on sabbatical.

This will carry through to Lab 4 and the iteration template.

This may help surface error handling issues for #762.