Add CompressJob.

This makes compressing work. The compress job is basically pure copy
job, which however copies to an empty archive instead of a directory.

Test: Tested manually. Unit tests coming.
Bug: 20822019
Change-Id: I5e661a398dc6daf61f69a386a490550a2e50069f
(cherry picked from commit e731da6d7dc46611e232ddee9a0f9b87d604ea44)
13 files changed