Grids with T other than the default Float64 are not constructed in a consistent manner

[navidcy]

There is a problem here:

FourierFlows.jl/src/domains.jl

Lines 116 to 120 in 1028120

	function TwoDGrid(nx, Lx, ny=nx, Ly=Lx; x0=-Lx/2, y0=-Ly/2, nthreads=Sys.CPU_THREADS, effort=FFTW.MEASURE, T=Float64,
	dealias=1/3)
	dx = Lx/nx
	dy = Ly/ny

If somebody prescribes

Lx=2π

as Float64 and then calls gr=TwoDGrid(nx, Lx, T=Float32), the resulting grid has

julia> typeof(gr.Lx)
Float64

while, e.g,

julia> typeof(gr.x)
Array{Float32,2}

I feel that the solution is to make sure Lx is typed correctly by adding

Lx = T(Lx)
Ly = T(Ly)

in the beginning of TwoDGrid function.

(Similarly in OneDGrid...)