Add global, modularized logging system

[darkf]

Format should be in e.g. "[Module] TYPE: Message"

For example: "[Scripting] WARN: Got bad value for [xxx]"

FWIW, logging/warnings/errors could use console.log/console.warn/console.error.

[darkf]

It's probably going to look something like this:

// At the top level of every module:

const log = Logging.logger("module name");

// ...

log.warn("test: %s", "foo"); // forwarded appropriately to console.warn

[darkf]

We can just take it from another project of mine, rrr, which I modelled in the same style: https://gitlab.com/darkf/rrr/blob/master/src/logging.ts