Infrakit App

[YujiOshima]

Discussed at #425

Infrakit 'app' is an application that can talk to the infrakit plugins using the plugin api but itself listens on a port and offers a REST api for operations like adding subscriptions, etc.

First of infrakit app will be repeater that is for events distribution to other hosts.
It repeats message from event plugin to other broker(mqtt) and from the broker to plugin.