Corrected coordinate computation in drawing a sphere/disk. Now centering also working when box has negative origin. Replaced DrawCircle.hpp by DrawDisk.hpp, because name circle misleading.

Deleted file GaussFilter.hpp. No longer needed. Problem with this form of gauss filter: weights do not exactly sum up to 1 due to rounding errors.

Deleted lines related to Gauss smoothing. The way the Gauss smoothing was done created problems, because the weights were not adding up to exactly 1 but had a round off error. Also Gauss smoothing is not really needed prior to the redistancing.