Spectators' tools, misc fixes, misc improvements

In this pull-request, I added a GUI used by the spectators to change their speed, from normal speed to Speed IV, and to enable the night/underwater vision (with the “Water Breathing” effect).

The fly speed is also changed.

Why the magma cream for the spectators' tools?
1. I think this item is beautiful.
2. This item is a “gradient” from the green (“on”) to the red (“off”). On/off, options. That's why.

![2014-09-15_17 40 07](https://cloud.githubusercontent.com/assets/1417570/4273870/c3fd975e-3cee-11e4-95cb-85f7a3252346.png)

I also changed the way the teleportation GUI is generated, to allow more that 27 players at the same time.

And, updating the potions effects to remove when the spectator mode is disabled, I changed a few more things to:
 - restore the potion effects instead of removing them;
 - restore the gamemode instead of using the default one.

[Build here](http://jenkins.carrade.eu/job/SpectatorPlus-AmauryCarrade/).