ffwizard-berlin: add support for private encrypted APs

see https://github.com/freifunk-berlin/firmware/issues/40 for more information.
ffwizard-berlin: add js to hide private ap form values if not enabled
ffwizard-berlin: add info section for private ap
Merge pull request #13 from freifunk-berlin/feature/private_encrypted_APs

ffwizard-berlin: add support for private encrypted APs