X-Debbugs-CC: sbaugh@janestreet.com
Tags: patch

This makes the return value of project--keymap-prompt include labels 
from the value of project-switch-commands (only those present - the 
other keys are printed without labels).

Seemingly makes it more readable, though longer.

This changes the 't' behavior, but if somebody really prefers the 
abbreviated version, we can make it a third value.