add new command line options: ws, wsbind, and wsapi

new command line options:
  --ws                    Enable the Websocket JSON-RPC server
  --wsbind:<value>        Set address:port pair(s) (comma-separated) Websocket JSON-RPC server will bind to (default: localhost:8546)
  --wsapi:<value>         Enable specific set of Websocket RPC API from list (comma-separated) (available: eth, debug)

fixes #770

nimbus/config.nim

@@ -126,6 +126,7 @@ type
     prune*: PruneMode
     graphql*: GraphqlConfiguration
     rpc*: RpcConfiguration        ## JSON-RPC configuration
+    ws*: RpcConfiguration         ## Websocket JSON-RPC configuration
     net*: NetConfiguration        ## Network configuration
     debug*: DebugConfiguration    ## Debug configuration
     customGenesis*: CustomGenesis ## Custom Genesis Configuration
@@ -462,6 +463,27 @@ proc processGraphqlArguments(key, value: string): ConfigStatus =
   else:
     result = EmptyOption
 
+proc processWsArguments(key, value: string): ConfigStatus =
+  ## Processes only `Websocket RPC` related command line options
+  result = Success
+  let config = getConfiguration()
+  let skey = key.toLowerAscii()
+  if skey == "ws":
+    if RpcFlags.Enabled notin config.ws.flags:
+      config.ws.flags.incl(RpcFlags.Enabled)
+      config.ws.flags.incl(defaultRpcApi)
+  elif skey == "wsbind":
+    config.ws.binds.setLen(0)
+    result = processAddressPortsList(value, config.ws.binds)
+  elif skey == "wsapi":
+    if RpcFlags.Enabled in config.ws.flags:
+      config.ws.flags.excl(defaultRpcApi)
+    else:
+      config.ws.flags.incl(RpcFlags.Enabled)
+    result = processRpcApiList(value, config.ws.flags)
+  else:
+    result = EmptyOption
+
 proc setBootnodes(onodes: var seq[ENode], nodeUris: openarray[string]) =
   var node: ENode
   onodes = newSeqOfCap[ENode](nodeUris.len)
@@ -677,6 +699,10 @@ proc initConfiguration(): NimbusConfiguration =
   result.rpc.flags = {}
   result.rpc.binds = @[initTAddress("127.0.0.1:8545")]
 
+  ## Websocket RPC defaults
+  result.ws.flags = {}
+  result.ws.binds = @[initTAddress("127.0.0.1:8546")]
+
   ## Network defaults
   result.net.setNetwork(defaultNetwork)
   result.net.maxPeers = 25
@@ -765,6 +791,9 @@ LOCAL SERVICE OPTIONS:
   --rpcapi:<value>        Enable specific set of RPC API from list (comma-separated) (available: eth, debug)
   --graphql               Enable the HTTP-GraphQL server
   --graphqlbind:<value>   Set address:port pair GraphQL server will bind (default: localhost:8547)
+  --ws                    Enable the Websocket JSON-RPC server
+  --wsbind:<value>        Set address:port pair(s) (comma-separated) Websocket JSON-RPC server will bind to (default: localhost:8546)
+  --wsapi:<value>         Enable specific set of Websocket RPC API from list (comma-separated) (available: eth, debug)
 
 LOGGING AND DEBUGGING OPTIONS:
   --log-level:<value>     One of: $2 (default: $3)
@@ -812,6 +841,7 @@ when declared(os.paramCount): # not available with `--app:lib`
             processArgument processNetArguments, key, value, msg
             processArgument processDebugArguments, key, value, msg
             processArgument processGraphqlArguments, key, value, msg
+            processArgument processWsArguments, key, value, msg
             if result != Success:
               msg = "Unknown option: '" & key & "'."
               break