move manifest* from imageloader to libbrillo We move them to libbrillo so it could be shared by imageloader&dlcservice. BUG=chromium:866203 TEST=unittest Change-Id: Id6e1f898d69c5cb1d4d291147482248ee3578f03 Reviewed-on: https://chromium-review.googlesource.com/1147249 Commit-Ready: Xiaochu Liu <[email protected]> Tested-by: Xiaochu Liu <[email protected]> Reviewed-by: Xiaochu Liu <[email protected]>