Use euclidean distance

In IterativeClosestPoint and SampleConsensusPrerejective, the distance given with setMaxCorrespondenceDistance()
is taken as euclidean distance, but in SampleConsensusInitialAlignment as square distance.

registration.getFitnessScore() takes the distance as square distance.

Changed SampleConsensusInitialAlignment and registration.getFitnessScore() to take distance
as euclidean distance.
Use euclidean distance - Fix tutorial

Fixed template_alignment tutorial (Set distance euclidean)

May be test_registration.cpp has to be changed also, but for the rest it seams that
getFitnessScore() is always called without argument and setMaxCorrespondenceDistance()
is not used anywhere else together with SampleConsensusInitialAlignment.