Spec updates for task and forall intents

* Changed syntax to 'with (...)'

* In the accompanying text, allowed any intents.

* In "craychapel" environment, indicated that only 'ref' intents are implemented and forall intents are not implemented and are upcoming.

* In "future" environment, removed the desire to have other intents. That's because we already provide them, as far as the spec is concerned.

* In "future" environment, mention that some intents may not make sense, e.g. 'out'.