Use a copy in place of mapMultiArgs["-addnode"].

Also moves the DNS lookup of -addnode nodes into the repeated
loop, allowing -addnode to follow DNS changes.
Make ThreadOpenAddedConnections2 exit quicker if(GetNameProxy()).
Add addnode RPC command.
Add a getaddednodeinfo RPC.
Try more than the first address for a DNS -addnode.
Merge pull request #1549 from TheBlueMatt/addnoderpc

Addnode optimization and addnode access via RPC