Add support for Splunk Metric Store

[n00badmin]

Add output format to allow easy integration with Splunk 7 metric store.

[n00badmin]

First pass on plugin update complete and PoC into metric store complete.

Still working on fine details and testing. Have successfully removed the need for lookups, making ingestion into Splunk easier. Will still work with event indexes as well.

[vvign]

First pass on plugin update complete and PoC into metric store complete.

Still working on fine details and testing. Have successfully removed the need for lookups, making ingestion into Splunk easier. Will still work with event indexes as well.

Is It available output format that support metrics store on Splunk?