Federated Graphite Support: carbon-{link,relay,aggregator} scaling across multiple nodes

This is my first try to implement the issue https://github.com/hw-cookbooks/graphite/issues/32. I tried to make the recipe backwards compatible. The changes are the following:

Application support:
* Added **carbon-replay** support.
* Added **carbon-aggregator** support.
* carbon-cache recipe separated from the main carbon recipe.

Configuration files:
* ~~carbon.conf updated.~~
* local_settings.py.erb to support cluster_servers and carbonlink_hosts variables.
* ~~**configurable storage-schemas.conf** support.~~
* Added **relay-rules.conf** support.
* Added **storage-aggregation.conf** support.
* Added **aggregation-rules.conf** support.

Other:
* Added whisper-clean helper script.
* Added a federated _application_ recipe example.
* Added bats tests for carbon-aggregator and federated recipes.
* ~~Some notifications added for service restarts.~~
* ~~The status in the _CentOS_ init scripts returns the correct status now.~~
* ~~Attributes separated into multiple files.~~