node: add InstanceDir method

node/node.go

@@ -601,10 +601,16 @@ func (n *Node) Service(service interface{}) error {
 }
 
 // DataDir retrieves the current datadir used by the protocol stack.
+// Deprecated: No files should be stored in this directory, use InstanceDir instead.
 func (n *Node) DataDir() string {
 	return n.config.DataDir
 }
 
+// InstanceDir retrieves the instance directory used by the protocol stack.
+func (n *Node) InstanceDir() string {
+	return n.config.instanceDir()
+}
+
 // AccountManager retrieves the account manager used by the protocol stack.
 func (n *Node) AccountManager() *accounts.Manager {
 	return n.accman