feat: bl-icon

[Hotell]

I'm submitting a ... (check one with "x")

[ ] bug report => search github for a similar issue or PR before submitting
[ x ] feature request
[ ] support request => You can submit support request here, but we preffer to chat about it realtime at our [ngParty slack](https://ngparty.herokuapp.com/)

Current behavior
we don't have any support for icons

Expected behavior
we need to create new component for rendering icons. this can be leveraged using composition with bl-button for instance

<bl-button>
   <bl-icon type="hamburger"></bl-icon>
</bl-button>

Inspiration:

https://material.angular.io/components/component/icon
https://github.com/developit/preact-mdl/blob/master/src/index.js#L208