Move WikiPageIniItem to core.

Moves the WikiPageIniItem to the main repo so I can use it in the about plugin.  Mostly copy paste, except adding the `_sr` property to `GoldPartner` and `GoldFeature` 

see https://github.com/reddit/reddit-public/pull/2347

:eyeglasses: @Deimos @spladug 
Nit: Ended up with a bit of a strange diff here because the new blank line has 4 spaces on it.