Add Manifest in order to include AUTHORS and ChangeLog

Unlike in master, where a different method for creating the
sdist tarball is used, we still need a MANIFEST.in here for
including AUTHORS and ChangeLog in the tarball.

Change-Id: I266b04048c383b4f127d336411937b102bfafab3
Fixes: Bug #979958
Merge "Add Manifest in order to include AUTHORS and ChangeLog" into stable/grizzly