New Feature: Allow adding nodes at runtime using RPC

this adds an RPC command to mincoind and mincoin-qt that allows the user to add remote nodes at runtime. This code does not interfere with the threading model in mincoin.

TODO: This will only work if the user did not set the max outbound connections above 125 AND the daemon has no more than 124 outbound connections. probably not a problem
TODO: added nodes are not persistant. while the original threading code renews outbound connections every 2 minutes, if yours breaks up the daemon will not automatically try to reconnect. not a big problem

Feature: adds the addnode rpc command that requires 1 parameter, which is either an IP address or a host name. RPC will return an error on addnode failure, or a success message on successful connect.