Added schema for x-nullable and description to some extensions. (#2677)
Added schema for x-nullable and description to some extensions. (#2677)


brjohnstmsft/autorest,olydis/autorest,fearthecowboy/autorest,jhendrixMSFT/autorest,jhendrixMSFT/autorest,Azure/autorest,fearthecowboy/autorest,jhendrixMSFT/autorest,Azure/autorest,jhendrixMSFT/autorest,Azure/autorest,olydis/autorest,Azure/autorest,brjohnstmsft/autorest