ask about loading conf-file on goto

after 70c6b2d, close-ycmd and then reverting and then M-. would show the
'load conf.py?' question in the warnings buffer
This should be renamed now to something like `ycmd--handle-unknown-extra-conf-exception`. The `notify` term denotes a specific bit of functionality, but now we're using this for both notify and goto. I was a bit confused at first!