First step - adding new WheelSlot params

[VzhelevVector]

Wheel Slot: media content attributes (Spec PR #305)

Implements mvrdevelopment/spec#305 — extends GdtfWheelSlot with four optional XML attributes for describing animated/video gobo media content.

Changes

Attribute	Type	XML name	Default
Duration	double (seconds)	Duration	0.0
Width	size_t (pixels)	Width	0
Height	size_t (pixels)	Height	0
FPS	size_t	FPS	0

All four attributes are optional and are only written to XML when non-zero/non-default.

Files modified

• src/Prefix/CommonPrefix.h — 4 new XML constants
• src/GDTFManager.h — private fields + getter/setter declarations on GdtfWheelSlot
• src/GDTFManager.cpp — constructor init, XML read/write, error check, getter/setter bodies
• src/Include/IMediaRessourceVectorInterface.h — 8 pure virtual methods on IGdtfWheelSlot
• src/Implementation/CGdtfWheelSlot.h — method declarations
• src/Implementation/CGdtfWheelSlot.cpp — method implementations
• unittest/GdtfUnittest.cpp — write + read-back assertions for all 4 attributes