Add code (including RNA wrappers) for:
- Creating, removing, and accessing `Animation` data-blocks.
- Creating and removing layers, strips, and outputs on those `Animation`
data-blocks.
- Accessing those via RNA.
Note that this does not include assignment to any animated data-block,
so it is of limited practical use.
For more info, see #113594.
Introduce new DNA for the `Animation` data-block and its sub-data.
This includes the blenkernel code for reading & writing to blend files,
and for memory management (freeing, duplicating). Minimal C++ wrappers
are included, with just the functionality needed for blenkernel to do
its job.
The Outliner code is extended so that it knows about the new data-type,
nothing more.
For more info, see issue #113594.