Blender Git Loki

Make global areas use properly managed screen-verts and screen-edges

* Added functions for ScrAreaMap to avoid code duplication
* Fixed loading files without top-bar not adding top-bar at all

Add ScrAreaMap struct wrapping screen-areas, -edges and -vertices

Global areas will need to use the edge and vertex lists in future too.
Once the topbar branch is merged, we can also change bScreen to use this
struct, avoiding code duplication.

Don't allow changing area into topbar editor, hide its menu item

We probably want to allow Python scripts to check if an area is the
topbar or later the status bar. Not sure if that'll work right now, I
can't test since global areas are not iterable through BPY at all.
Maybe that's fine too ;)

Disable toolshelf redo regions for now

Inteded to do that in rB223f4fa583cb386 already, but forgot to comment
out again after testing...

Don't write topbar data into files (yet)

We decided to do this so we don't have to care much about compatibility. The
code for writing is just #ifdef'ed out so it can easily be brought back.

Bring back toolshelf redo region, ifdef'ed out though

Just for until the design is better defined. Also moved SpaceTopBar
struct to a better place in its DNA file.

Only remove info editors on top of the window using the full width

Removing all info editors could cause issues. Wanted to get proper
layout resolving to work, but wasted more than an entire day on that.
Still planning to look into that again though.

Fixup for last merge

Merge branch 'blender2.8' into topbar

Merge branch 'blender2.8' into topbar

Initial working drag & drop for workspace tabs

Had to do quite some changes to get this to work, mainly because we'd
want to have the customized order written to files. Also wanted to use
existing wmDrag and wmDropBox code but modify it for our needs.
And of course, this should not just work for a single case, code should
be applicable to other areas as well.

Note that file read/write is not working (yet), neither is versioning, region
copying and deleting workspaces working.
Code is also very WIP, much of it is placed in temporary places and
such.

Once the basics are done, we can add nicer feeback during drag & drop.

Merge branch 'blender2.8' into topbar

Merge branch 'blender2.8' into topbar

Merge branch 'blender2.8' into topbar

Merge branch 'blender2.8' into topbar

Merge branch 'blender2.8' into topbar

Merge branch 'blender2.8' into topbar

Merge branch 'blender2.8' into topbar

Merge branch 'blender2.8' into topbar

Fix issues in .py after last merge