* Convert all log levels to lowercase
* Make number of threads configurable
* Improve naming
* Update path and log options for Logstash 2.4
* Change worker count from string to integer for the Kafka output plugin supplied
  with Logstash 2.4.

Partially-Implements: blueprint monasca-roles
Change-Id: I9379969ee639dff0b525d7a1a03df59bcf18b98b