rpc: various fixes/enhancements

rpc: be less restrictive on the request id
rpc: improved documentation
console: upgrade web3.js to version 0.16.0
rpc: cache http connections
rpc: rename wsDomains parameter to wsOrigins

cmd/geth/usage.go

@@ -94,7 +94,7 @@ var AppHelpFlagGroups = []flagGroup{
 			utils.WSListenAddrFlag,
 			utils.WSPortFlag,
 			utils.WSApiFlag,
-			utils.WSAllowedDomainsFlag,
+			utils.WSAllowedOriginsFlag,
 			utils.IPCDisabledFlag,
 			utils.IPCApiFlag,
 			utils.IPCPathFlag,