Fix missing API docs

See https://github.com/openlayers/ol3/pull/2479#issuecomment-51438681.

Removes attribution#tileRanges as suggested, and adds `@api` for others. Two are not addressed here: `ol.format.Feature` and `ol.render.IVectorContext`. These are parent classes, already in the api docs, and AFAICS are only referred to as types in private methods. I'm not sure what needs to be done here - should they be template types (`T`)?