Expose all formater as services

Right now, it's not damn easy to configure a custom formatter
for an handler, because the developer should create a new service.
Right now, only for formatter not does not depend on external
configuration, we can use directly monolog formatter:

   heka:
       type: socket
       connection_string: "%heka_endpoint%"
       timeout: 1
       connection_timeout: 1
       formatter: monolog.formatter.json_formatter