Add LabelShapeStatisticsImageFilter

This filter is a wrapper to the
LabelImageToShapeLabelMapFilter. There is not image output. Instead of
the LabelMap provided by the original filter, this SimpleITK filter
provides access to the resulting statistics as members through the
active measurements system.

Change-Id: I843dc9dd66db1867e71e82838b22a11609294422
Use custom_methods for additional accessors to label list

Change-Id: I593be25f197b8f488a5f62daec7018871bf843cd
Add testing of measurements for LabelShapeStatistics

Change-Id: If6c4045d25fa41e0357c21acc66e56f140477e24
Merge topic 'SIMPLEITK-516_AddLabelShapeStatisticsImageFilter' into next

5479470b Add testing of measurements for LabelShapeStatistics
b15e6a13 Use custom_methods for additional accessors to label list
0ea72335 Add LabelShapeStatisticsImageFilter