Change erosion to a 2D slicewise

[jcohenadad]

The current script: Outside.in_Erosion.Script.sh is performing a 3D kernel operation, which produces partial volume.

To fix that: we need to switch the operation to a 2D erosion.

Things to check/fix:

• redefinition of selem variable in erosion/dilation kernel.
• use the iteration feature from scikit-image to get multi-step erosion