Added extra flag to control whether InfluxDB should be started on install. Templates use 'influxdb' group when joining cluster, so all influxdb instances that need to be clustered must be part of that group (previously it was using all hosts).

Variables moved from vars/main.yml to defaults/main.yml.  Role variables that you wish to optionally override in inventory should be in defaults.

Variable names have been namespace to role as to not collide with other roles using similar names.

Templates and tasks have been update to use new variable names.