What title(s) should a one-person film crew receive in the credit role?
Sounds like you directed it. Would be simple to just put Director, I think one can assume you did everything then if there is no editor or DP credited.  

The director is responsible for the overall vision of the flow of the piece.  They oversee filming and work with a cinematographer, if applicable, to determine the right look for the film, work with actors to get the right performance and then work with the editor to make sure it flows.  They are basically the person chiefly responsible for adapting the screenplay or concept of the film in to a finished movie.

For Example:

If you create a documentary completely by yourself, lets say you spend 20 days in Antarctica, you film everything you narrate, when you get back you edit it, and then do sound and music.  At the end of the day you directed that documentary, which for all intensive purposes is the highest credit you could receive, if the film ends and says directed by x.  People watching are not going to stand up and go "Wait who shot this film?" It is implied that you did it since you directed it and nobody was credited under you.

Another way this is sometimes credited to avoid confusion is simply doing created by