Add a slicer module that exports single image slices with segmentation

[ungi]

This is needed because 3d segmentation-based export only works when the segmented structure doesn't move relative to the reference coordinate system. In human scans, almost every internal structure moves a bit during scanning.

[lassoan]

Probably for this it would be good to have a Sequence Segmentation module, which would help setting up segmentation sequence (synchronized with the input image sequence) and some tools to help with propagating segmentation between time points (e.g., using intensity based registration). This module could also have an export feature to save both input image sequence and corresponding segmentation.

This module should be probably in the Sequences extension.

[ungi]

That would be great!