BLC: Start DKG on Add/Remove only needed for common coin

[jeanphilippeD]

One section of the RFC cover changes to start the DKG on Add/Remove of peers. This will likely be essential for Common Coin, and has code mostly implemented in the common-coin branch.

However, it is not required for only routing using BLS, and seem to have a significant impact in the behavior of Parsec and Malice detection.
So to limit risk we should probably postpone implementing/integrating that part.

https://maidsafe.slack.com/archives/C03DZQTKU/p1559900615256700?thread_ts=1559896007.250100&cid=C03DZQTKU (maidsafe internal link)