Remove cdn support

Signed-off-by: Tilman Vatteroth <git@tilmanvatteroth.de>

app.js

@@ -191,7 +191,6 @@ app.engine('ejs', ejs.renderFile)
 // set view engine
 app.set('view engine', 'ejs')
 // set generally available variables for all views
-app.locals.useCDN = config.useCDN
 app.locals.serverURL = config.serverURL
 app.locals.sourceURL = config.sourceURL
 app.locals.allowAnonymous = config.allowAnonymous