Database of all errors

[stevekrouse]

Related to #491

We already happen to have a database of every version of saved code. For multiplayer/team code, we have every keystroke. So if we wanted to go searching for common errors, this could be a place to start. We could take the text of the code and statically analyse it for errors for starters. (Running the code to test for runtime errors probably wouldn't be worth the effort.)

The other approach is to shoot off a request to a database log of every error (runtime and static) that we catch from users on woofjs.com. This could be a good time to test out Firebase's new database engine. Probably only a ~20 hour project. We'd want to send the full text of the source code and all data from the error message itself.

A sensible first analysis would simply be grouping error messages by their message and seeing which are most common and confusing. That way we'd know which to try to explain better in #491.