Add Ability to not send a specific release to Rally on Master Feature or Feature

Rally has a concept of Backlog where the Release is set as 'Unscheduled'.  But there is no way in Aha! to assign a Master Feature or Feature to something like 'Unscheduled' so that the Release information does not get populated in Rally.  We want to keep the integration setup to pass the release information on the Master Feature and Feature, but would like to have the ability to denote on a Release (or something) that this particular release information is unscheduled and shouldn't be assigned to the Master Feature/Feature in Rally.