Pluggable error logging

[m1h43l]

Currently escape message are handled in ileastic.c serverThread function caught by the exception handler and passed to handleServletException which returns a 500 message to the client.

It is currently not possible to somehow log the escape message. It would be great if we could have an interface to get all necessary information on a not handled escape message so that we could write individual plugins to handle this information f. e. log it somewhere.