* First pass at making 'private' work on include_role, imports are always public
* Prevent dupe task execution and overwriting handlers
* New functionality will use public instead of deprecated private
* Add tests for public exposure
* Validate vars before import/include to ensure they don't expose too early
* Add porting guide docs about public argument and change to import_role
* Add additional docs about public and vars exposure to module docs
* Insert role handlers at parse time, exposing them globally
