D11361: add a version containmentForScreen with activity

[Marco Martin]

mart added a dependent revision: D11801: remove m_desktopContainments.

REPOSITORY
  R242 Plasma Framework (Library)

REVISION DETAIL
  https://phabricator.kde.org/D11361

To: mart, #plasma, davidedmundson
Cc: davidedmundson, #frameworks, michaelh, ngraham