Created by: vicdoval
Performance upgrade: Creating Bmesh before matching lengths boost performance over 2x when slicing the same object with many matrices.
To perform the fewest bmesh_from_pydata the conversion is done in the SvRecursiveNode mixin so other bmesh-based nodes can also benefit from it.
Also: Recursiveness upgrade (multilevel length matching) Clean Output option to remove empty objects. Simplify Output options: - Flat: Flattens last level of objects (old behaviour and default) - None: Leave untouched - Join: Join last level of objects
- 
Code changes complete.  - 
Code documentation complete.  - 
Documentation for users complete (or not required, if user never sees these changes).  - 
Manual testing done.  - 
Unit-tests implemented.  - 
Ready for merge.