getWork needs to return additional values

common/common.go cleanup

using robertkrimen/otto, godeps updated

Conflicts:
	eth/backend.go

* WIP missing arguments for submitting new work
* GetWork **done**

Frontier/blockpool 

- logjson flag remove logformat flag
- passed to eth Config
- logsystem not a field of Ethereum
- LogSystem does not need to expose GetLogLevel/SetLogLevel
- message struct just implements more generic LogMsg interface
- LogMsg is a fmt.Stringer with Level()
- jsonMsg ([]byte) implements LogMsg
- remove "raw" systems
- move level logic inside StdLogSystem
- logsystems only print their kind of msg: jsonLogSystem prints jsonMsg, StdLogSystem prints stdMsg

- fix status chain map uses common.Hash as key
- add badPeers increment to IncorrectTD errors (forgotten)
- signal head info update to head section process even if parent hash is not in pool (inserted), so that idle timer can be set to nil
- suicideC -> peer.headInfoTimer
- quit -> peer.bestIdleTimer
- and they are properly set from within getBlockHashes and handleSection

Fix link to build instructions in the readme

Conflicts:
	rpc/responses.go