Blender Git Loki

Depsgraph: support flushing parameters without a full COW update

Avoid computationally expensive copying operations
when only some settings have been modified.

This is done by adding support for updating parameters
without tagging for copy-on-write.

Currently only mesh data blocks are supported,
other data-blocks can be added individually.

This prepares for changing values such as edit-mesh auto-smooth angle
in edit-mode without duplicating all mesh-data.
The benefit will only be seen when the user interface no longer tags
all ID's for copy on write updates.

ID_RECALC_GEOMETRY_ALL_MODES has been added to support situations
where non edit-mode geometry is modified in edit-mode.
While this isn't something user are likely to do,
Python scripts may change the underlying mesh.

Reviewed By: sergey

Ref D11377