Add support for checkmk agent plugin 'smart'

[jkirk]

The following checks need the checkmk agent plugin smart:

• smart_stats
• smart_temp

We should support these checks so this role should be able to deploy the agent plugin smart.
It seems reasonable to enable the plugin by default (on Debian hosts), similar to mk_apt. (What do you think, @mika?)

Upstream code can be found here: https://github.com/tribe29/checkmk/blob/master/agents/plugins/smart

Note, the plugin makes use of smartctl and/or(?) megacli. The(se) tool(s) should be deployed where needed (this is not scope of this role, though). /cc @mika

[mika]

It certainly makes to provide an easy™ option to deploy the smart_ plugins, but we should keep in mind, that it's only supposed to be deployed on physical servers (non-VMs), and systems with HW RAID controllers might not work as-is. So maybe deploy by default on physical systems, but make it easy™ to disable that feature if needed?