2nd Vertcoin P2Pool network for small miners

This release introduces a second Vertcoin p2pool network designed for smaller miners, perhaps with only one or two GPUs who those do not mine frequently (ie miners are not running 24/7). The existing p2pool network has grown to be quite large, making it hard for smaller and infrequent miners to get a share. This new network can be accessed via the flag --net vertcoin2. Those who have dedicated VTC miners should continue to use the existing network.