Blender Git Loki

Fix T41062: "copy to selected" doens't work for all attributes.

The issue was that some properties are no direct children of the struct we support in 'copy to selected'
(RNA_Sequence in this case). Since we can't use the ID of sequences here (it's the scene, while we need
a sequence level of control), we had to add a new API helper to RNA path, which takes a RNA type
and return a path relative to the closest ancester of that type.

This way, we get a path from the RNA_Sequence, and can easily apply it to all other valid sequences
to copy the property.

Review, suggestions and edits by Campbell Barton, thanks!