Blender Git Loki

Alembic: export object data with object data name

The old exporter always exported a mesh object to `{object.name}/{object.name}Shape`. Now it exports to `{object.name}/{mesh.name}` instead. The same change also applies to other object data types.

Note that the code now is a bit hackish, as `m_name` is set even in cases where it isn't used. This hackishness was already there, though, but it's now just more visible. This will all be cleaned up when the Alembic exporter is ported to use the `AbstractHierarchyImporter` structure of USD.

Differential Revision: https://developer.blender.org/D7672