Add/use template for browsing layout-types of a workspace/window combination

Tried adding a more generic template for this first, but this is really
such a special case that it would need to have quite a bunch of
exceptions.
Basically we're showing the active layer-instance of the workspace in
the text button and within the menu, the layout-type list of the
workspace and their previews from the screen wrapped by the
layout-instance :S

Also made renaming work properly.

Make fullscreen toggling work again

This still creates a new screen which would be nice to avoid, but quite
some logic depends on the creation of this screen, so leaving it there
for now.

Fix drawing glitch in inactive windows after addin layout

Was drawing area edges but not areas itself, had to manually trigger
redraws.
Also some cleanup, it doesn't make much sense to return some layout of
the bunch of ones that have been created.

Don't create workspace or screen-layout when opening temp windows (e.g user prefs)

Not sure how safe change in area.c is, had to do that to avoid weird
scroll offset when opening user pref window.

Merge branch 'blender2.8' into temp-workspace-multi-window

Fix mistake in 2301dd18a36d5

Apparently I didn't test correctly before pushing :|

Get duplicating area into new window to work

We don't duplicate the workspace or the layout-type anymore. We just open a
new window with the same workspace and same layout-type.

Solve subwindow console warning

Completely get rid of per-window data duplicates from workspaces

Fix crashes closing windows or Blender itself

Show the correct list of screens in the info editor

Work towards completely moving workspace data to window level

Stuff is starting to work out!

Make screen-layouts of duplicated windows much less broken :)

There are probably still some issues/glitches after duplicating a window
here and there, but most of it should work fine by now.

Don't copy workspace when copying window

This kinda works, however screens are still completly broken after that
:) But: getting there!

Fix broken screen-setups after creating workspaces or layouts

Cleanup: Style, remove unused function, use wrapper struct for arguments

Wrap screen-layout data into own struct

Makes it easier to pass around.

Fix crash when changing workspace

There are more issues when changing workspaces and I think I know
how to fix them, but it may need some further changes.

Make duplicating workspaces work

Fix errors in areabase/vertbase storage