ECOG Randomized Phase III Study of Maintenance Therapy with Bevacizumab; Pemetrexed; or a Combination of Bevacizumab and Pemetrexed Following Carboplatin; Paclitaxel and Bevacizumab for Advanced Non-Squamous NSCLC Adult CIRB - Late Phase Emphasis Closed to Accrual. Pts Still Rcving Intervention Available to Open