Add PoCo Overview

This is some thoughts about the API and Frontend implementation related to #106, the output looks like this:
![Screenshot](https://i.imgur.com/fVTrY5F.png)

* it consumes the API for PoCo into an extra table
* reads the location info of the next Planet (just like with the nearest moons for Starbases)
* in the view you can see the actual PoCo config
* permission level is set to `pos_manager`

It may not be pretty, but will be giving an overview to those with a few PoCo's

Feedback is welcome :+1: 
Should be for `CorporationController@getCustomsOffices`