Ability to disable polling of systems

Middleware components finished. There is a new "connection_paused" field for the servers/[add/edit/list] API calls which will control this behavior.

Release Council decision:
The option to "pause" a system connection and treat it like an unsupported NAS version should be good enough.

The statistics gathering is the entire "brain" of the control systems within TrueCommand as well. If there is no stats, then there is nothing that the UI can access to provide control mechanisms.

That being said, we do have the ability for you to change the polling interval for your systems. This should allow you to set an arbitrarily long polling period to ensure TrueCommand management does not impact performance testing of your NAS, but TC will still do the initial probe of the system stats so we have system state data for doing other management interactions.

There will probably be state/caching issues if the polling interval is increased too much though, so we will need to look into this and see if there are some limitations or optimizations we can do to "minimize" polling without completely disabling it.