Read/write color property between MRML nodes and respective SMTK components.

Copy origin, spacing, and orientation matrix of MRML segmentation
nodes to SMTK image. This was not done previously, causing spatial
mismatch of segmentation image with extracted geometries.

Read/Write colors, names, and orientation of segmentations
correctly. Each segmentation will be saved as a vtkImageData labelmap,
which implies that segments are mutually exclusive. Overlapping
segments will overwrite each other. To preserve overlapping
segments, user must create separate segmentation nodes in Slicer.