PLT-3408 Add SiteURL to config.json (#3692)

* PLT-3408 Changed serverside code to get the service's URL from config.json

* PLT-3408 Changed most clientside code to use the SiteURL config setting instead of window.location

* PLT-3408 Changed default SiteURL to be autodetected

webapp/components/create_team/components/team_url.jsx

@@ -105,7 +105,7 @@ export default class TeamUrl extends React.Component {
             nameDivClass += ' has-error';
         }
 
-        const title = `${Utils.getWindowLocationOrigin()}/`;
+        const title = `${window.mm_config.SiteURL}/`;
         const urlTooltip = (
             <Tooltip id='urlTooltip'>{title}</Tooltip>
         );