Update Dialog function comments
Update Dialog function comments

Dialog function comments are updated for clarification, consistency, and improved support with Jazzy.

tad-iizuka/swift-sdk,watson-developer-cloud/ios-sdk,tad-iizuka/swift-sdk,watson-developer-cloud/ios-sdk,tad-iizuka/swift-sdk,tad-iizuka/swift-sdk,watson-developer-cloud/ios-sdk,watson-developer-cloud/ios-sdk,watson-developer-cloud/ios-sdk,tad-iizuka/swift-sdk