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 <xiaochu@chromium.org>
Tested-by: Xiaochu Liu <xiaochu@chromium.org>
Reviewed-by: Xiaochu Liu <xiaochu@chromium.org>
4 files changed