Fix settings and documentation for remote_debug role

-- To use, enable this role from shell:
   vagrant enable-role remote_debug
-- In your IDE, enable "Start Listening for PHP Debug Connections"
-- For firefox, install
   https://addons.mozilla.org/en-US/firefox/addon/the-easiest-xdebug
   and click "Enable Debug" icon in the Add-on bar
-- Set breakpoints
-- Navigate to localhost:8080/...

Change-Id: Ib3e1e5799664a5ed79b42ba350fd78ed890d7f8a
Merge "Fix settings and documentation for remote_debug role"