More config options

Introduced:

- [:graphite][:base_dir] and removed all hardcoding of /opt/graphite in recipes/templates
- [:graphite][:graphite_web][:http_port] to change the vhost port
- [:graphite][:graphite_web][:addtional_vhost_configt] to add configuration to the default vhost Location/

--> this is useful for example to integrate it with tasseo that requires you to add some Access-Control-Allow-Origin to overcome Cross Side Scripting security