Rename "DDNP" to "Dickens Notes" across project

[annamgibson]

In keeping with our "rebranding" of the project, rename DDNP to "Dickens Notes" across the project, including in the navigation menu. @grenerad we should chat about this and confirm that this is what we want to do.

[grenerad]

Yes, I agree we should enact this renaming. It is probably significant enough of a change that we should make it part of a new version (and not just do it). The changes should be straightfoward enough, but the changes to the Nav. bar and drop downs might create formatting issues or require other changes that we would want Scott to check (not tagging him here now but we can in due course).