Log Message:
Changes 1.9.0:
* Flexible incremental computation of image and region statistics via Feature \ 
Accumulators and corresponding Python bindings (see \ 
vigra.analysis.extractFeatures() and vigra.analysis.extractRegionFeatures()).
* Simultaneous iteration over several arrays via vigra::CoupledScanOrderIterator.
* Import and export of images with transparency: importImageAlpha() and \ 
exportImageAlpha().
* Image denoising by total variation filtering, see Non-linear Diffusion and \ 
Total Variation and example total_variation.cxx.
* Fixed Python bindings of Unsupervised Decomposition.
* Extended vigra::SplineImageView to handle vigra::TinyVector pixels.
* Various convenience functions for vigranumpy's VigraArray.
* Minor improvements and bug fixes in the code and documentation.