Expose enum class PickupAndDeliveryPolicy in all languages

[Mizux]

Currently we have

or-tools/ortools/constraint_solver/routing.h

Lines 217 to 227 in 0b7ba4f

	#ifndef SWIG
	// Types of precedence policy applied to pickup and delivery pairs.
	enum class PickupAndDeliveryPolicy {
	// Any precedence is accepted.
	ANY,
	// Deliveries must be performed in reverse order of pickups.
	LIFO,
	// Deliveries must be performed in the same order as pickups.
	FIFO
	};
	#endif // SWIG

We should expose it to all languages so customer can use it in their prefered language.

• Add C++ Samples
• Remove SWIG guard from routing.h on enum class PickupAndDeliveryPolicy
• Update Python swig file
  • Add Python Samples
• Update Java swig file
  • Add Java Samples
• Update .Net swig file
  • Add .Net Samples
• Update pdp.md doc

[Mizux]

related to #922