Spike generic flow structure

[jvalkeal]

Currently all build-in components are simply hard coded into a flow structure. Study what it would take to make it generic so that a custom component could be used with it.

[tschut]

This would be really useful. For instance, I've extended StringInput to support validation (which seems like it would be a useful feature in itself btw), but now I can't use this component in a Flow.

Is this an area where contributions are welcome?