New compatability with the schema changes in MemSQL Ops

Test Plan: inspection

Reviewers: chase

Differential Revision: http://grizzly.memsql.com/D4056
Extracted collectd plugin into a seperate library: memsql-collectd

Summary: https://github.com/memsql/memsql-collectd

Test Plan: inspection

Reviewers: chase

Differential Revision: http://grizzly.memsql.com/D4063
better cleanup
Release version 2.8.0

 - Major change: Moved MemSQL collectd plugin to new package:
 memsql-collectd