3d removal of background

https://www.notion.so/qim-dtu/3D-remove-background-function-fac8e64da886429eacd9520bc7be0610?pvs=4

implemented into existing filters framework

qim3d/processing/__init__.py

+from .detection import *
 from .filters import *
 from .local_thickness import local_thickness
+from .operations import *
 from .structure_tensor import structure_tensor
-from .detection import *