RZFInteractionDelegate contract is strange

[bskinner]

The delegation implementation in RZFUpgradeManager has several issues which could lead to confusing behavior when used, and present consumers of the library with difficulties if they want alternate behavior. The current behavior of the RZFUpgradeManager is:
0. If nothing is currently presented, a single UpdatePrompt or ReleaseNotes modal can be presented

1. An UpdatePrompt modal may dismiss a currently presented ReleaseNotes modal
2. When presenting an update message, if an UpdatePrompt modal is already presented, do nothing.
3. When presenting a release notes message, if either a UpdatePrompt or ReleaseNotes is currently being presented, do nothing.

This logic should be moved out of the RZFUpgradeManager and into the default interaction delegate.