Updates to the conceptual model to separate app operator and developer roles

[dumbnose]

This is the change to the conceptual model that we discussed last week. I didn't update every single page to reflect this change. I wanted everyone to first see the proposed adjustments before changing any additional references to the concepts. So, please take a look and provide feedback. I'll be on vacation for the next week. So, I won't be able to react to any changes until I get back. Thanks.