CDK-451: View isReady / signalReady

This PR builds on https://github.com/kite-sdk/kite/pull/98 and https://github.com/kite-sdk/kite/pull/99 adding support for isReady / signalReady on Views.
I don't think this is true because it depends on the partition function used. For example, the range partitioners always produce a set of potential partition values, so we can enumerate the values that match a range. We can also do that for simple integer or long partitions, although there may be quite a few of them.

I don't think this is something we need to fix to get the signalling in, but I'd prefer a weaker name for this method that is more accurate.