Fixes the "java.lang.IllegalStateException: Cannot forward after respons...

Fixes issue [#98].
When an anonymous user without a token accesses an anonymous endpoint.
It was giving a 500 and throwing "java.lang.IllegalStateException: Cannot forward after response has been committed"
It now gives a 200.

- The main issue was in the BearerTokenReader as it was sendingError, 
- Moved all the error handling logic to the BearerTokenAuthenticationFailureHandler
[#98]