Registrar and contractInfo handling

* resolver -> common/registrar
  * global registrar name registry interface
  * add Call to resolver backend interface
  * the hashReg and UrlHing contracts now initialised from global registry
  * initialization of contracts uniform
  * improve errors and more econsistent method names
* common/registrar/ethreg: versioned registrar
* integrate new naming and registrar in natspec
* js console api: setGlobalRegistrar, setHashReg, setUrlHint
* js test TestContract uses mining - tests fixed all pass
* eth/backend: allow PoW test mode (small ethash DAG)
* console jsre refers to resolver.abi/addr,
* cmd/geth/contracts.go moved to common/registrar