cli: clean up flag descriptions, usage docs, account list uses primary and indexes, add help line to account subcnd usage

* Disabled on CLI
* http://localhost on Mist

- etherbase flag for block reward destination
- coinbase => etherbase
- CLI- eth Config -> eth, xeth -> RPC / Miner
- use primary instead of coinbase as the unlock magic wildcard
- accounts: firstAddr/Coinbase -> Primary

- remove account export functionality from CLI
- remove accountExport method,
- remove unencrypted-keys flag from everywhere
- improve documentation

output error message if unlock address is invalid (fixes the wierd "read /path: is a directory") msg

- accounts: remove Manager.getKey
- cli: for -unlock coinbase, use account manager Coinbase()

- extract accounts.getKey method - if given empty address it retrieves coinbase (first account)
- cli -unlock coinbase will unlock coinbase

- cli: add passwordfile flag
- cli: change unlock flag only takes account
- cli: with unlock you are prompted for password or use passfile with password flag
- cli: unlockAccount used in normal client start (run) and accountExport
- cli: getPassword used in accountCreate and accountImport
- accounts: Manager.Import, Manager.Export
- crypto: SaveECDSA (to complement LoadECDSA) to save to file
- crypto: NewKeyFromECDSA added (used in accountImport and New = generated constructor)

- 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