Skip projection formats without a %s

This allows us to expand the option in the future without breaking
backwards compatibility.
Fix turnip template
Allow explicitly specifying projection command

This lets you have the description in the error message different from
the command name, and also lets you disable the command (but still get
other projection features) by providing an empty string.
Increase priority of config/editor.json

This makes config/editor.json and g:rails_default_config take precedence
over :Rnavcommand and :Rabbrev.