Improved comments, split up role, moved tags and added defaults

- Added some commenting inside of defaults to clarify which variables
  adjust which files

- Split up the role taking items out of main.yml in tasks. This is to
  improve clarity of what each bit of Ansible code is doing.

- Tags were defined for each and every task within the Debian.yml moved
  ths up to main.yml so they don't need repeating every task adding
  clutter.

- Added some extra default plugins, as of current release version these
  are now within the default configuration but were missing from this
  role.

- Added some commenting inside the templates and the top of some tasks
  to clarify where the templated file was coming from.

defaults/main.yml

@@ -30,6 +30,7 @@ telegraf_agent_output:
       - database = "telegraf"
       - precision = "s"
 
+# defaults - /etc/telegraf/telegraf.conf
 telegraf_plugins_default:
   - plugin: cpu
     config:
@@ -41,8 +42,12 @@ telegraf_plugins_default:
   - plugin: system
   - plugin: swap
   - plugin: netstat
+  - plugin: processes
+  - plugin: diskio
+  - plugin: kernel
 
-telegraf_plugins_extra:
+# extra configuration - /etc/telegraf/telegraf.d/*
+telegraf_plugins_extra: []
 
 # RedHat specific settings for convenience
 telegraf_redhat_releasever: "$releasever"