[Thresholding Operator] Issue 910

This fixes #910. I was not able to fix the issue directly, so I had to replace `OpAnisotropicGaussianSmoothing` with a fully 5d compatible version. There are still some unresolved problems with the combination of `OpMultiArrayStacker` and `OpCompressedCache`. This does also depend on ilastik/lazyflow#142, otherwise `OpLabelVolume` will have the same problem.

I tested this on Ubuntu 14.04 -- if you have got another platform please test it there, too.

This could also solve #913, but I need to verify that first.