Update templates on DEB upgrade

This change will cause the Web and DNS templates to be refreshed/updated when upgrading via the DEB package. 

To-do: Add OS detection or fix path so it's not hard-coded to Ubuntu 18.04.

src/deb/hestia/postinst

@@ -68,4 +68,7 @@ if [ ! -z "$BACKEND_PORT" ]; then
     /usr/local/hestia/bin/v-change-sys-port $BACKEND_PORT
 fi
 
+# Update Web and DNS templates
+cp -rf /usr/local/hestia/install/ubuntu/18.04/templates/* /usr/local/hestia/data/templates/
+
 exit 0