Basic Pool Environment Creation

[jaiden-lee]

• Added empty pool: 4 walls, floor, 9 lane markers
• Pool dimensions: 50m x 25m x 3m
• Added light source to allow for shadows
• Wall and floor colors = off white/grey
• Lane markers: navy blue

[mroglan]

I've added Matthew as a reviewer as well since he is most familiar with the simulation. Also closes #12.

[jaiden-lee]

I think underwater.sdf was just purely expiremental. If so, can we delete it?

Yeah I forgot to delete it my bad