Add PointNormal to ExtractIndices Instantiate Types

[UnaNancyOwen]

This pull request will add pcl::PointNormal to instantiate types of pcl::ExtractIndices, because this type is missing even though there are pcl::Normal and pcl::PointXYZRGBNormal.
It is no longer necessary to separate point cloud to pcl::PointXYZ and pcl::Normal when want to use pcl::ExtractIndices with pcl::PointNormal. You can use pcl::ExtractIndices<pcl::PointNormal> directly.