Implement SSL security for mcollective

Rework mcollective::* classes attributes to be more fine-grained:
    - Rename broker-related attributes as $broker_*
    - Rename security-related attributes as $security_*

  Add support for SSL security support in classes and templates

  Add mcollective::client::certificate

:warning: This PR renames the attributes for `mcollective::client` and `mcollective::node`!