[apps] Deal with aliases in PointCloud Editor app

[aPonza]

After #3753, the PointCloud Editor app has mixed references to pcl::shared_ptr and std::shared_ptr due to the existence of the file localTypes.h. I believe the best course of action would be to remove:

pcl/apps/point_cloud_editor/include/pcl/apps/point_cloud_editor/localTypes.h

Lines 69 to 91 in 336f192

	/// The type for std shared pointer pointing to a cloud object
	using CloudPtr = std::shared_ptr<Cloud>;
	/// The type for std shared pointer pointing to a constant cloud
	/// object
	using ConstCloudPtr = std::shared_ptr<const Cloud>;
	/// The type for std shared pointer pointing to a selection buffer
	using SelectionPtr = std::shared_ptr<Selection>;
	/// The type for std shared pointer pointing to a constant selection
	/// buffer
	using ConstSelectionPtr = std::shared_ptr<const Selection>;
	/// The type for std shared pointer pointing to a copy buffer
	using CopyBufferPtr = std::shared_ptr<CopyBuffer>;
	/// The type for std shared pointer pointing to a constant copy
	/// buffer
	using ConstCopyBufferPtr = std::shared_ptr<const CopyBuffer>;
	/// The type for std shared pointer pointing to a command object
	using CommandPtr = std::shared_ptr<Command>;

and

pcl/apps/point_cloud_editor/include/pcl/apps/point_cloud_editor/localTypes.h

Lines 100 to 102 in 336f192

	/// The type for std shared pointer pointing to a command queue
	/// object
	using CommandQueuePtr = std::shared_ptr<CommandQueue>;

from the file and deal with the ruckus of every other file using that one in the app. This means using the same strategy of the referenced PR and introducing in-class aliases like e.g.:

class Cloud : public Statistics
{
  public:
    /// The type for shared pointer pointing to a selection buffer
    using SelectionPtr = pcl::shared_ptr<Selection>;

    [...]
};

[SergioRAgostinho]

I honestly have no preference, because it's not really part of the API. Pick whatever you feel its best and try to enforce it consistently for this particular app.