/series/add: fields are hidden and links for showing them don't work when JS is disabled

Reported by @Shkarin and extracted from https://github.com/php-coder/mystamps/pull/547#issuecomment-295443129:

![fce746440ccd4c06b93d08eef0f07789](https://cloud.githubusercontent.com/assets/87088/25269813/8bbb3758-267e-11e7-97dd-9ddf7b18bc96.png)
