Tasks review.
Logstash example: mapping timestamp by its keyword.
Task added.
Typo fix. Update example comments.
Agile sink factory has been implemented.

Now you can register own sinks via `sink_factory_t` class.
Configs are moved into separate files.
Oops, copy/paste bug.
Adapt to new configs.
Drop unused constructor.
Minor cleanup.
One task less.
Sink names are now part of class definition.
Minor parameters reducing.
Formatter registration has been implemented. Now they have own names.