### Feature and motivation

Adding parameter for subpath configuration so inside container application can work on different path than root.

I've tested rewrite rules on ingress and they do not work correctly.

### Usage example

Currently application works on http://localhost:4444 inside of the container, unfortunately in ingress implementation with reverse-proxy application will not respond correctly to ingress configuration where path is configured different than "/"
New parameter would allow to change base URL of the application to work on http://localhost/selenium:4444 which will allow correct communication with ingress.
}
  @Override
  public String getDescription() {
    return "A grid hub, composed of sessions, distributor, and router.";
  }
  @Override
  public Set<Role> getConfigurableRoles() {
    return ImmutableSet.of(
      DISTRIBUTOR_ROLE,
      EVENT_BUS_ROLE,
      HTTPD_ROLE,
      SESSION_QUEUE_ROLE,
      ROUTER_ROLE);
  }
  @Override
  public Set<Object> getFlagObjects() {
    return Collections.emptySet();
  }
  @Override
  protected String getSystemPropertiesConfigPrefix() {
    return "selenium";
  }
  @Override
  protected Config getDefaultConfig() {
    return new DefaultHubConfig();
  }
  @Override
  protected Handlers createHandlers(Config config) {
    LoggingOptions loggingOptions = new LoggingOptions(config);
    Tracer tracer = loggingOptions.getTracer();