Renamed NODE_COUNT to POOL_SIZE because now the number of nodes is different from the number of nodes which are actively validating. However, I'm not sure what the naming convention is here, so would be happy to change it.
Added finalized_dynasties which is used to check if we can choose new validators
This PR adds dynamic validator set logic as defined in this blog post: https://medium.com/@VitalikButerin/safety-under-dynamic-validator-sets-ef0c3bbdf9f6#.iviyb6u3y
Changes
NODE_COUNTtoPOOL_SIZEbecause now the number of nodes is different from the number of nodes which are actively validating. However, I'm not sure what the naming convention is here, so would be happy to change it.finalized_dynastieswhich is used to check if we can choose new validators