Validation of exception handler - handlers must not throw exceptions

As stated in the deltaspike documentation, exception handlers must not throw checked exceptions, and should avoid throwing unchecked exceptions.

Handlers must not throw checked exceptions, and should avoid throwing unchecked exceptions. Should a handler throw an unchecked exception it will propagate up the stack and all handling done via DeltaSpike will cease. Any exception that was being handled will be lost.

I checked that throwing exceptions from handler really causes problems.

I suggest to add validation which could display error when user attempts to throw checked exception and warning when try to throw unchecked exception.