Adding terrain & water

Terrain create and code for water added.
#issues: null pointer from LWJGL when loading scene with assets manager.
Complete

Done: Basic terrain (smooth, single texture), post process water,
ambient light, sun light.
Terrain extended

Done: Added multiple terrain texture to the asset pack. Terrain
texturing added with blending.
Skybox

Done: Created skybox using a dds, changed light direction to shine from
moon in skybox.
TODO: find a way to flip the skybox by 180
DayNight system attempt

This branch is created in an attempt at creating a changing day night
sky box system with moving stars and clouds.
@Issue: getting a null pointer for lwjgl when creating skybox.
DayNight system working

Implemented with basic settings and functionality.
@TODO:
Time of day change in render update.
Scene light change in render update.
Test adding bloom filter.
Test setting changes.