AI 146237: ADT #
1789339: Manifest editor now displays all extra sub-elements.
Bug description is to add support for <uses-configuration>.
Currently the Manifest editor already supports <uses-sdk> (which is an
element node, not an attribute) by exposing it as a manifest attribute.
That doesn't scale. So instead just provide a tree for all <manifest>
child elements that are not handled in other pages. Currently that
contains uses-sdk and uses-configuration but the nice part of it is that
it will pick up automatically any new manfiest sub elements in the future.
BUG=
1789339
Automated import of CL 146237