Add graceful shutdown and error handling

[Octalbyte]

This PR adds handling for fatal crashes of any type. Just so you don't have to see a giant error stack on your console.
The feature is turned on by the --no-panic option or by the environment variable NODE_HTTP_SERVER_NO_PANIC. The output is something like:

Relevant issues

Refers partly to #665

What needs to be done:

• [x] Add switch.
• [x] Better log file (JSON formatting)

Contributor checklist

• [x] Provide tests for the changes (unless documentation-only)
• [x] Documented any new features, CLI switches, etc. (if applicable)
  • [x] Server --help output
  • [x] README.md
  • [x] doc/http-server.1 (use the same format as other entries)
• [x] The pull request is being made against the master branch

Maintainer checklist

• [ ] Assign a version triage tag
• [ ] Approve tests if applicable

[Octalbyte]

Ready for review.