static interface for permutedims

I would like to contribute an implementation for permutedims, but first I would like to ask for suggestions about the interface.

In particular, it would be ideal if one could encode the permutation statically. I could imagine a

struct StaticPermutation{N}
    permuation::NTuple{N,Int}
    ## optionally: constructor that verifies validity
end

type and an interface like

permutedims(sarray, StaticPermutation(2, 3, 1))

but I am interested in suggestions if there is a better solution.

Start with the existing permutedims implementation in src/abstractarray.jl at the linked location, then review the proposed StaticPermutation{N} interface in the issue. The work is not ready for implementation until the interface is agreed on; done would mean a decided static permutation API and an implementation plan.