Making FeatureRep and Variation public

[ghost]

We have interest in using the InMemoryFeatureStore for testing and local development purposes, however the public API of the store (for writing values) depends on the default scope (package private) FeatureRep<E> class.

Looking at history the previous reason was to "Give reps default scope so they don't pollute javadoc" (see: 765db3d).

Is this still a strong enough reason to make them default scoped? Is there something better we could do other than making reps public?

This change also makes Variation<> public for similar reasons.

Edit: Okay a bunch of other stuff fell forward with this change - I also made Variations, TargetRules and their associated Builders public.

Quite a bit ended up changing here - if wish to keep these package private I will perhaps look at other options to solve our use cases (like for example; adding a FeatureStore which takes a map of key values instead).

[jkodumal]

I think we need to look at other options, unfortunately. We will want to reserve the ability to change the internal representations of feature flags without having to do major client releases. Let me know if you want to have a conversation about other ways to solve your use cases.

[ghost]

No worries. I will submit another potential solution in the form of a new FeatureStore which will keep reps private.