Code cleanup: Delete custom AsyncTask, ViewHolder, and Target files, and other bug fixes

Post recommendations in the UpdateRecommendationsSerivice, not the RecommendationBuilder.
Delete custom ViewHolder in CardPresenter.java.
Delete PicassoImageCardViewTarget in CardPresenter.java.
Delete DetailRowBuilderTask in LeanbackDetailsFragment.java.
Only remain visible behind launcher when video is playing.
Delete PicassoBackgroundManagerTarget.java.