Merge branch 'blender2.8' into id_override_static

Merge branch 'blender2.8' into id_override_static

ID static override: add basic support for overriding animation.

This is very bold right now - you simply can replace (or add) an action
to an override data-block. Actions themselves are not 'customizable'
through override at all currently (we may at least add
'add/remove/replace fcurves' feature in future), and nothing else in
animdata is overridable currently.

Make basic object & bones transformations overridable.

You can now override loc/rot/scale of objects and posebones.

Also added a basic operator to make an override of active linked object,
but this is very limited/wip/testing feature (you have to manually override
object and its armature, and relink to proper local overrides
yourself...). Final 'make proxy killer' will be much more automated of
course.

ID static override: Make most Image properties overridable.

First real 'usable' commit, will be needed by the 'virtual data-block'
asset feature (i.e. to be able to link a mere image file as if it was a
linked datablock, and generate automatically an override of it to make
it editable).

ID static override: automatically detect new overrides as part of undo step.

We could do that in several different way, e.g. adding some tag during
DEG evaluation, etc. But this is not a critical process (it's main
purpose is user feedback), so current solution seems to work well enough
- and it's dead simple! ;)

ID Static Override: add basic generic UI tools to control override of properties.

ID Static Override: add basic UI feedback.

For now, using a new color for overridden properties (similar to
animated/driven status), UI team will need to work on a better solution
maybe...

ID Static Override, part II: RNA changes.

This is essentially a huge refactor/extension of our existing RNA
compare & copy code, since static override needs more advanced handling here.

Note that not all new features are implemented yet, advanced things like
collections insertion/deletion are still TODO (medium priority).

This completes the ground work for overrides, remaining commits will be
about UI and some basic/testing activation of overrides for a limited
set of data-blocks & properties.

For details see https://developer.blender.org/D2417

Define RNA_STACK_ARRAY (usable everywhere in RNA), and make PYRNA_STACK_ARRAY use it.

Merge branch 'blender2.8' into id_override_static

Conflicts:
source/blender/blenkernel/intern/library_override.c

Merge ID static override, part I: core changes in DNA, BKE and .blend read/write.

See https://developer.blender.org/D2417 for details.

Note that since static overrides rely heavily on RNA, this commit is
essentially invisible from user PoV, more in next commits.

Merge branch 'blender2.8' into id_override_static

Preparing merge of id_override_static: add BKE_id_swap().

This function swaps the memory content of two data-blocks (of same type
obviously), while preserving most of the ID 'header' itself.

It is intended to be used to quickly and easily replace the data of an
existing ID by another one, presumably a temporary 'working' one,
without having to suffer from things like name changes,
registering/removing from Main database, etc.

Merge branch 'blender2.8' into id_override_static

Rename 'override' to 'override_static' (and similar).

Initially there was hope at least part of this work could be used for
dynamic overrides as well... but looks like not, so better be specific
and avoid any confusion.

PS: this commit break any file saved with static overrides, should not
be an issue though.

Address review points (mainly some missing usages of RNA_STACK_ARRAY).

Merge branch 'blender2.8' into id_override_static

Cleanup: remove timer-like check for auto-ID-override generation.

Merge branch 'blender2.8' into id_override_static