Added a function to get a colored cloud of segmentation

- Added a way to copy data from return variable clusters to internal variable clusters_ in order to use it later on.
- Added the implementation of the function getColoredCloud() in class EuclideanClusterExtraction to view a colored cloud of the segmentation result.
This looks overly complicated to filter the vector. I haven't looked through the file, but if we can't filter upon insertion to the vector, we could ``std::remove_if`` and last, we could use ```std::vector::swap``.