With all Platforms using `AbstractOutput` now, the next goal is to replace the `Screens` class with something more integrated, either in `Platform` directly or as a separate output manager.
... looking at the code this will actually be somewhat bigger. So here is a first plan:
* X fullscreen cleanup: D18128 D18132 D18153 D18157
* Remove legacy X multi-head and Xinerama support.
###New Outputs global connecting Platform and Workspace levels
* Replace `Screens` class with `Outputs` global class being created in `Platform` and directly accessed on `Workspace` level.
* `Outputs` features getters for all and only enabled outputs and does this by just calling into `Platform`.
* Through these getters `Workspace`-level classes access `AbstractOutput` properties directly.