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.~~