Carousel building with Kotlin DSL - Step 1

[eboudrant]

This is a refresh from @elihart's pull request #850 about issue issue #847.

While we certainly need a more robust api so we could use the DSL for custom carousel (and Epoxy model) group I propose we do it step by step.

Where the first step is we merge this change :

• Create a ModelCollector with required change in code-gen
• Add an example of builder in the sample app EpoxyCarouselNoSnapBuilder.kt
• Update the sample app to use the carousel DSL

carouselNoSnap { 
  id(...)
  models(mutableListOf<CarouselItemCustomViewModel_>().apply {
    for (...) {
      add(
        CarouselItemCustomViewModel_()
          .id(...)
        )
      }
  })
}

carouselNoSnapBuilder {
  id(...)
  for (...) {
    carouselItemCustomView {
      id(...)
    }
  }
}

[elihart]

Great :)

[ameyab10]

@eboudrant Thanks for the PR :)