Map Editor and new Desert environment

New things:

- The MapEditor is finally ready, so new maps can be built pretty quickly with some visualizing! :)

Gameplay:

- New Desert environment has been created with an oasis and some rocks, dunes and a sand "storm"(-ish) particle system.

- The 5 currently available day cycles (Day, Night, Stormy, Cosmic and Alien Dawn) have their lightning and particle system set and one of them can be selected on the map selector screen.

- One more light source added to enhance the visibility of the gameplay area when needed (mostly in darker day cycles, like Cosmic or Night).