this is needed to be able to test classes independently. All these sub classes inherit from the base class (::fluentd). If you call these classes directly you will get a duplicated declaration error.
this class overwrites the installation default 'td-agent.conf' with and include of the created '/etc/td-agent/conf.d' directory. All sources, matches and filters will be placed as single files in '/etc/td-agent/conf.d'.