Make CoreId a class in its own right.

	* Debug/src/subdir.mk: Added CoreId.
	* Release/src/subdir.mk: Likewise.
	* src/CoreId.cpp: Created,
	* src/CoreId.h: Created
	* src/GdbServer.cpp: Replace uint32_t addresses by CoreId
	throughout.
	* src/GdbServer.h: Likewise.
	* src/TargetControl.h: Likewise.
	* src/TargetControlHardware.cpp: Likewise.
	* src/TargetControlHardware.h: Likewise.