* PREVHASH => BLOCKHASH( N )
* State transition object uses VMEnv as it's query interface
* Updated vm.Enviroment has GetHash( n ) for BLOCKHASH instruction
* Added GetHash to xeth, core, utils & test environments
- new flag nat for nat support UPNP|PMP
- new flag pmp for PMP gateway IP
- add NatType to utils/cmd to get p2p.NAT from nat type string
- obsolete usepnp flag
- get rid of IsUpToDate and sleep in miner start
- ethereum constructor takes nat type, port, maxpeer
- add pubkey arg to client identity
- eth p2p pkgs
- new Ethereum initialiser
- no caps param
- use nat type
- add NatType func to map nat type string to p2p.NAT
- add pubkey to client identity
* Miner has been rewritten
* Added new miner pane
* Added option for local txs
* Added option to read from MergeMining contract and list them for
merged mining