Make enums CaseIterable

[denizdogan]

I'm not sure if this is actually possible, but can we make the generated enums conform to CaseIterable? The use case here is that I have a list of images in my preview assets for testing purposes, and I need to put them in a long list. Without CaseIterable, I need to manually make the array of images.

[mickeyl]

I can certainly see a use case for that. Merging https://github.com/kaandedeoglu/Shark/tree/namespaced_color_assets would be a requirement though, since it contains a refactoring towards a common enum builder.

Unfortunately this no longer applies cleanly, as I started my work on the framework-specific code generation without knowing of the existence of this very branch.

[denizdogan]

@mickeyl I thought it would be enough to just add a configuration option here, similar to #44? Kind of like --case-iterable would slap CaseIterable onto every enum?

[mickeyl]

@denizdogan I figured we can just conform unconditionally to CaseIterable. We don't need it for the localizable strings though, or do we?

[denizdogan]

@mickeyl Not as far as I know

[mickeyl]

This is now life as per the 1.6.0 release.