TODO-List for gmapping (and partly explore)
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open:
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1. implement a working(!) ancestry tree 

2. compute trajectory uncertainty based on the 
   ancestry tree formula

3. possibility to choose the way the pose uncertainty
   for a particle set is computed (grid vs set of
   gaussians)

4. Fix the NAN Problem with the pose uncertainty with gaussians
   
done:
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(move the done stuff down here)