* Rename GenericArgs to AuthRPCArgs
* Rename GenericReply to AuthRPCReply
* Remove authConfig.loginMethod and add authConfig.ServiceName
* Rename loginServer to AuthRPCServer
* Rename RPCLoginArgs to LoginRPCArgs
* Rename RPCLoginReply to LoginRPCReply
* Version and RequestTime are added to LoginRPCArgs and verified by
server side, not client side.
* Fix data race in lockMaintainence loop.
This change adds more richer error response
for JSON-RPC by interpreting object layer
errors to corresponding meaningful errors
for the web browser.
```go
&json2.Error{
Message: "Bucket Name Invalid, Only lowercase letters, full stops, and numbers are allowed.",
}
```
Additionally this patch also allows PresignedGetObject()
to take expiry parameter to have variable expiry.
