Broadcasting `Fields`

[albert-de-montserrat]

Fields are compatible with broadcasting, but with the current behavior it returns an Array:

julia> N    = 16;
julia> arch = Arch(backend);
julia> grid = UniformGrid(arch; origin=(0, 0), extent=(1, 1), dims=(N,N));
julia> launch = Launcher(arch, grid);
julia> C = Field(backend, grid, Center())
2D 16×16 Field{Float64} located at (Center, Center)
julia> (C.*C) |> typeof
Matrix{Float64} (alias for Array{Float64, 2})

It would be nice if it returned a Field instead.