one-liner installer added for shot ref for Dockerfiles
debugger event-handler added

serf agent --event-handler=/usr/local/serf/handlers/debugger --log-level=debug
debugger added permanently its only viewable when --log-level=debug specified
event handler which can generate bash test-function to test a handler
by default its not activated you have to use as:
serf agent  --event-handler=/usr/local/serf/handlers/test-function-generator
use 1 liner install so ADD can be later, this way rebuilding can skip instalment