* InvalidParameter: New error type
* Return inaccessible for 5xx errors from services
* Add test for Inaccessible on 5xx
* Add tests for named error types
Make a clear distinction between programmer errors ("internal errors") and runtime errors, and allow configuring the server to let the programmer errors bubble up in development and unit testing. This saves a huge amount of time because it generates ordinary stack traces when things go wrong. And, if these errors occur in production, we'll catch them, and display **shields | internal error** which is the equivalent of a 500 error.
