Consider Deprecating Optional Booleans

[emorydunn]

The plugin manifest makes extensive use of optional booleans, such that not including the value uses the default. This makes sense for hand-edited JSON, but for generated manifest it means almost every action attribute is option, which is a little odd in Swift.

Instead these properties should be marked as non-optional with a default implementation providing the SDK default value. This will also simplify the user's code, as they won't need to have a bunch of unused properties.