Improve core config validation

[adubovik]

Currently there are a lot of arbitrary parsed JSON strings in the Core config schema.

We need to make the schema more strict, to fail fast in case of incorrect configs.

A couple of examples:

1. Pricing.unit is of type String, whereas it must be enum with "tokens" and "char_without_whitespace" cases;
2. Deployment.name is of type String, whereas it must be a string matching pattern [^/]+ (see ControllerSelector);
3. Deployment.iconUrl is String, whereas it must a be a valid URL.

And many more...