Econ improv

This revives the first half of #1197 (all changes in `SystemInfoView.{cpp,h}`). I added analysis of illegal goods as well, and think I fixed the bug @Luomu mentioned in that PR, , with the econ tab not updating after hyper jump:

> I flew from Sol to Proxima Centauri, docked at a station and the econ screen still says "Commodity trade analysis of Proxima Centauri against Sol (current system)". I have to click on a new target on the Sectorview to correct this.

with commit d0d6d6367ea60beec8f9ee124a3fe3c49a45848a.

It works as mentioned in my first (two) posts on the [dev forum](http://pioneerspacesim.net/forum/viewtopic.php?f=3&t=251&sid=5a4b5c3e6cb2808f8a692d083b55df40)

It also adds translated strings, and mouse over tooltip.

![image](https://cloud.githubusercontent.com/assets/619390/3701967/70016518-13f9-11e4-94f9-e7f13898b922.png)
This is the first time I done anything in this file, so this is a part of the code I'm not 100% on. 

The text here in `m_commodityTradeLabel` never shows up in the game , so it could/should? just be an empty string instead? I assume it's because the string is always replaced by `UpdateEconomyTab()`