Add cleanup handlers

[bwachter]

Some roles, like web servers, generally should provide includes for other roles to easily add to the webserver configuration. Problem there is that this is not compatible with the role taking control of all configuration files - it won't know which files got added as includes during the main role run.

To fix this, and avoid an ordering mess, roles should be able to register cleanup callbacks into basic_host to be run at the end of the play, which allows removal of files not touched by any role during the run.