Inventory GUI

Added the inventory GUI.

Illustration: 
![2014-09-05_00 00 29](https://cloud.githubusercontent.com/assets/1417570/4158293/38688652-348a-11e4-9ee9-22ac1ab34a10.png)
*(Here displayed with a small change to display my own view on every right-click, to be able to test it in solo.)*
See the source code for the titles & tooltips.

I also added a possibility to see this view from the teleportation menu.
![2014-09-05_01 08 02](https://cloud.githubusercontent.com/assets/1417570/4158298/4aa5396e-348a-11e4-8d56-e688f312da5b.png)

I also changed the name of the players in the teleportation menu (I use the display name, and I reset the color before to avoid the italic formatting).

Currently, in the title of the inventory view, the pseudonym is the display name.
In your opinion, should I use this display name, or, more sober, the name (to have a title without extra formatting)?

Also, should I remove the central water separator on the last line, to have only one separator, in your opinion?

Last point, I added the option to change the item used, but the option is not implemented, because I suppose you already know how you want to implement it :) .