Remove Blender Internal and legacy viewport from Blender 2.8.

Brecht authored this commit, but he gave me the honours to actually
do it. Here it goes; Blender Internal. Bye bye, you did great!

* Point density, voxel data, ocean, environment map textures were removed,
as these only worked within BI rendering. Note that the ocean modifier
and the Cycles point density shader node continue to work.
* Dynamic paint using material shading was removed, as this only worked
with BI. If we ever wanted to support this again probably it should go
through the baking API.
* GPU shader export through the Python API was removed. This only worked
for the old BI GLSL shaders, which no longer exists. Doing something
similar for Eevee would be significantly more complicated because it
uses a lot of multiplass rendering and logic outside the shader, it's
probably impractical.
* Collada material import / export code is mostly gone, as it only worked
for BI materials. We need to add Cycles / Eevee material support at some
point.
* The mesh noise operator was removed since it only worked with BI
material texture slots. A displacement modifier can be used instead.
* The delete texture paint slot operator was removed since it only worked
for BI material texture slots. Could be added back with node support.

* Not all legacy viewport features are supported in the new viewport, but
their code was removed. If we need to bring anything back we can look at
older git revisions.
* There is some legacy viewport code that I could not remove yet, and some
that I probably missed.
* Shader node execution code was left mostly intact, even though it is not
used anywhere now. We may eventually use this to replace the texture
nodes with Cycles / Eevee shader nodes.

* The Cycles Bake panel now includes settings for baking multires normal
and displacement maps. The underlying code needs to be merged properly,
and we plan to add back support for multires AO baking and add support
to Cycles baking for features like vertex color, displacement, and other
missing baking features.

* This commit removes DNA and the Python API for BI material, lamp, world
and scene settings. This breaks a lot of addons.
* There is more DNA that can be removed or renamed, where Cycles or Eevee
are reusing some old BI properties but the names are not really correct
anymore.
* Texture slots for materials, lamps and world were removed. They remain
for brushes, particles and freestyle linestyles.
* 'BLENDER_RENDER' remains in the COMPAT_ENGINES of UI panels. Cycles and
other renderers use this to find all panels to show, minus a few panels
that they have their own replacement for.

This copyright text (copied to binary distros) had a confusing statement about
scripts being "Artwork" which is your sole property and free to license.

I've removed the reference to scripts in this text.

This was from 2002! With our Python scripts becoming part of how Blender runs,
such scripts now are officially required to be compliant with GNU GPL.

For more information; check the FAQ or consult [email protected]
https://www.blender.org/support/faq/

This copyright text (copied to binary distros) had a confusing statement about
scripts being "Artwork" which is your sole property and free to license.

I've removed the reference to scripts in this text.

This was from 2002! With our Python scripts becoming part of how Blender runs,
such scripts now are officially required to be compliant with GNU GPL.

For more information; check the FAQ or consult [email protected]
https://www.blender.org/support/faq/

And here is the first git (testing) commit by me!
Welcome to a brave new GPL3 world... well if commit works :)

Bugfix #35920

Adding a new node in Node Editor failed for "High DPI" (Only Mac retina now).

- Py script for adding nodes was doing dpi magic, which it shouldn't. It has
been replaced with a (temporary) API call to set the correct cursor location.
(Thanks to Lukas T for helping here)

- The SpaceNode->cursor[2] property now is *only* storing the coordinate
in "adding new node space". Use of this has been removed from the code where
possible, with as only exception the code to draw noodles while adding them.

Special coder note: Nodes should respect the DPI value, and draw larger with
larger buttons if you increase this size. The hack here is that this can only
work nice if also the node positions are scaled accordingly.

A better fix could be to check on scaling the node view itself for it. That
then would also remove this Python API call that was added in this commit.
However, that again might fight with how buttons layout code works now...
needs some careful checking.

Bugfix #36324

Commit 57760, June this year, broke Theme colors for Label Buttons.
All labels, in every editor or region, now were using same color.

These colors have to be derived from the Editor settings. Code for
this was mistakingly removed.

GPL V3 license, which will be valid for the binary releases.
(Because Blender links with the Apache2 license).

Cleanup of this directory will happen before official release.

Tradtional release commit! 2.68 splash and the numbering.

- This should then follow the tagging
- And I would still prefer to have at least 24 hours full freeze, for proper test
and avoid last minute errors.

Usability:

For users without middle-mouse buttons, they can now use Circle and Border
deselect by holding SHIFT. Middle mouse still works too.

Bug fix #35749

Image Editor: "Replace Image" operator didn't refresh icon for image.