Trigonometric polynomial spaces

[vpuri3]

• full fourier
• sines
• cosines

option to evolve in transformed space or physical space. make associated boundary conditions clear

[vpuri3]

struct TransformedSpace
    space
end

function transform(space::FourierSpace)
    TransformedSpace(space)
end

function transform(space::TransformedSpace)
    space.space
end