find redundant adding of identical keys to the key list in PFHEstimation buffer
find redundant adding of identical keys to the key list in PFHEstimation buffer

Closes #1243. Fixes #1189.

ipa-rmb/pcl,ipa-rmb/pcl,stefanbuettner/pcl,drmateo/pcl,ipa-rmb/pcl,drmateo/pcl,drmateo/pcl,ipa-rmb/pcl,drmateo/pcl,stefanbuettner/pcl,stefanbuettner/pcl,stefanbuettner/pcl,stefanbuettner/pcl,drmateo/pcl,ipa-rmb/pcl