This will add functionality to automatically load ES plugins

This will setup and load any ES plugins and parses the configuration options for it
It also adds the client ( node, transport ) options to the configuration hash
Merge pull request #3 from logstash-plugins/feature/support_es_plugins

This will add functionality to automatically load ES plugins
Update elasticsearch output to respect the 'index'

Now the elasticsearch output plugin will respect the
'index' plugin setting and override the default index
template to update the indexes it matches on based on
the 'index' setting.

Any placeholders ("%{...}") will be translated to '*' so the
template matching pattern is generic and in line with elasticsearch
wildcarding.