This PS allows users to specify the manifest file to use
by the Armada handler by introducing a new flag called
`target_manifest`. This flag was added to the API and
CLI.
A foundation of unit tests for the manifest handler
is included in this PS. Most of the coverage is aimed
at checking the various success and failure cases
surrounding the new target_manifest feature.
Also updates documentation to convey information about
the new flag and clean up some documentation formatting
inconsistencies and typos.
Change-Id: I1d5a3ecc1e99b6479438d0ee5490610178be34fe
093b5d2296