Support for arrays of textures #822

I just wanted to get the ball rolling on support for arrays of textures in shaders. Coming from this issue on the wgpu-rs repo: gfx-rs/wgpu#106

The idea is to be able to use an array of 2d textures in shaders, as originally shown in the issue above:

layout(set = 0, binding = 1) uniform texture2D textures[1024];