Ref T12450. This mostly just smooths out the text a little to improve consistency. Also:

• Use isWritable().
• Make the "skipping because not writable" message more clear and tailored.
• Try not to use the word "index" too much to avoid confusion with bin/search index -- instead, talk about "initialize a service".

Ran bin/search init with a couple of different (writable / not writable) configs, saw slightly clearer messaging.