Ahodges/documentation/doc158

@WatsonEmily please share with PMs who have worked through this process with data czars before... I'd love to get their feedback on level of detail and completeness.
@rocha and @stroilova , please let me know if this information is accurate (or designate others in Analytics).
@mhoeber and @srpearce , your feedback always welcome.

Setting up the keys is next in this chapter.  Can you suggest ways to make this clearer?