avoid HTML escaping in JSON files

[matthias314]

Currently the HTML characters "<" and ">" are escaped in the JSON file micro writes, see here. This makes the bindings.json file hard to read: Instead of

{
    "<F5><a>": "command:log",
}

one gets

{
    "\u003cF5\u003e\u003ca\u003e": "command:log",
}

This PR changes this. I'm assuming that the HTML security concern behind the escaping doesn't apply here. For settings.json I don't have a strong use case. I just thought it's best to use the same code for both files.