DescribingElems: configuring over XML

The node DescribingElems contains a list of nodes that will be created using the plugin loader for Descriptors

Possible Descriptors are currently:

<ShapeModel>

<CalTab>

<Blob>

<ColorClass>

<DeformShapeModel>

<SegmentPrototype>

<DetectedFace>

<TransparentObject>

<TransparentObject>

see also <SigDBRoot>