Dynamic pipeline configuration using file reloading

Currently there is no way to enable or disable meters without restarting ceilometer. There are cases where operators do not want to run all the meters continuously.

By enhancing Ceilometer to monitor pipeline file configuration, the application could be made to dynamically activate/deactivate meters, collection targets or similar functions, have distinctly different configurations for multiple nodes in different environments (i.e. dev/test/prod or HA scenarios) and could ultimately be updated with new collection targets “on-the-fly”.