Add ComponentData

[JamesEdgeley]

Add ComponentData class

[JamesEdgeley]

@SMijin this is approximately the feature I need for the 2D3V reflection

[SMijin]

I was thinking this could go in the ExtractorData as an optional argument, i.e. the current extraction takes the first N components, but there could always be an offset there, as well. So your ComponentData would just be ExtractorData<1> with the appropriate offset. This way one could take any number of consecutive components.

This would make it easier to repurpose existing tests, but would also require some doc changes. I can look at this in a few weeks.