only add images to watchlist view in alpha (alpha, 376)

note although the story specifies images should show in beta
in preparation for moving watchlist to stable i'm adding to alpha only

* add alpha class to body tag when in alpha mode
* add alpha to getConfig

Change-Id: Ie27f1fdd5bc096d9e0f034484f2c0e1f380f8158
Merge "only add images to watchlist view in alpha (alpha, 376)"