logging: output is unnecessarily excessive

As a JavaScript developer, default log output feels excessive.

The default log level is what I'd consider approaching `silly` log leveling in terms of how [npm does log levels](https://docs.npmjs.com/misc/config#loglevel), which has largely guided the direction of JavaScript logging.

Some specific cases where the logging feels excessive:
- In 99% of cases so far, I've not needed date/time in any log. For those I do need, I'd be more than happy to run with an additional flag to get those additional 20 characters per line.
- The hot reloading functionality of Azure Functions is awesome but my entire terminal gets filled with messages about the restart.
- There's a non-trivial amount of JSON output to the console, in addition to dozens of stats messages and host context that I don't need as a developer just writing a function.

Each of these unfortunately train me to ignore my console rather than pay attention to it.

It would be nice to see the ability to more directly control log output through levels, with the current setting being equivalent to or just below npm's `silly`.