Consider renaming fields

[mvahowe]

As well as field names that are inconsistent, and in separate issues, some names could maybe be clearer. Changes like this need to be rare (because they break client applications) and need to be coordinated (because the names need to work together across the graph). So let's list some ideas here as a first step towards a pre-1.0 renaming spree.

[mvahowe]

cIndex, cvIndex and cvIndexes should probably be called something more informative, since the most common use case is to get content, not the index itself.