Support X-Forwarded-Host name for proxy

Change-Id: I50b11be093cd63217e685f6dccecad9fcdbc0898
diff --git a/kalamar.conf b/kalamar.conf
index ee35197..714c32b 100644
--- a/kalamar.conf
+++ b/kalamar.conf
@@ -39,6 +39,9 @@
     ## Backend API version
     # api_version => '1.0',
 
+    ## If the application is run behind a proxy, ignore the forwarded host
+    # proxy_host => 0,
+
     ## Run the application in a subfolder behind a proxy:
     # proxy_prefix => '/korap',