Add documentation on advanced use for manipulating data layout

[jatkinson1000]

Removed from being part of #20 we should add some information for advanced users about manipulating data beyond simple transposition using the 'stride' options, as was done by @jatkinson1000 and @SimonClifford in the MiMA-ML project.

## Advanced use

Those experienced with C will perhaps have noticed that there are further freedoms
available beyond those presented above.

Always stride, or is there a transpose tradeoff?