Auto-scaling capabilities

[frbattid]

This issue comes from an offline conversation with QA people ( @iariasleon ).

It would be useful if Cygnus auto-scales the number of processing sinks or the size of the channels. The decission about how to grow up the system may be limited by a certain threshold.

It is known Flume reloads in a pediodic fashion the configuration file, thus once decided the new number of sinks and/or the new channels size, it seems as simple as automatically writing the apropriate configuration.