Added support for quashing url status messages.
Added support for quashing url status messages.

This add the `ycmd-hide-url-status` flag. When set to true (default),
this prevents the `url` package from displaying status messages. This
effect is only traffic to ycmd; for other traffic, url status is
displayed (or not) as configured.

ptrv/emacs-ycmd,phst/emacs-ycmd,abingham/emacs-ycmd,emacsmirror/ycmd,phst/emacs-ycmd,phst/emacs-ycmd,phst/emacs-ycmd,emacsmirror/ycmd,ptrv/emacs-ycmd,ptrv/emacs-ycmd,emacsmirror/ycmd,abingham/emacs-ycmd,phst/emacs-ycmd,ptrv/emacs-ycmd,ptrv/emacs-ycmd,abingham/emacs-ycmd,emacsmirror/ycmd,emacsmirror/ycmd,phst/emacs-ycmd,abingham/emacs-ycmd,abingham/emacs-ycmd,ptrv/emacs-ycmd,abingham/emacs-ycmd,emacsmirror/ycmd