Definition of gridpoints() and its tests

[jbytecode]

gridpoints() was originally defined as

function gridpoints(x::Vector{T}, y=x::Vector{T}, z=x::Vector{T}) where T<:Real
    reshape([GeometryBasics.Point{3, T}(x, y, z) for z in z, y in y, x in x], 
                             length(x)*length(y)*length(z))
end 

but it can be simplified like this

function gridpoints(x::Vector{T}, y=x, z=x) where T<:Real
    reshape([GeometryBasics.Point{3, T}(x, y, z) for z in z, y in y, x in x], 
                             length(x)*length(y)*length(z))
end 

A test suite is added to avoiding any breaking changes. expected values are obtained by the original code. The changed code produces the same output.

[Kevin-Mattheus-Moerman]

Great thanks!