Update docs for Sections and Views
Update docs for Sections and Views

Summary:
Specs are required by the annotation processor to end in `Spec`, and renamed confusing `Edge` postfix to `Event`.
Closes https://github.com/facebook/litho/pull/319

Differential Revision: D7028412

Pulled By: passy

fbshipit-source-id: 1c47d82f0d9dafc3a38487457ddd19b8a5c4a191

facebook/litho,facebook/litho,facebook/litho,facebook/litho,facebook/litho,facebook/litho