SiSpacePointsSeedTool_xk: Comply with ATLAS naming conventions.

...k/SiSpacePointsSeedTool_xk/SiSpacePointsSeedMaker_ATLxk.h

...SiSpacePointsSeedTool_xk/SiSpacePointsSeedMaker_BeamGas.h

.../SiSpacePointsSeedTool_xk/SiSpacePointsSeedMaker_Cosmic.h

...iSpacePointsSeedTool_xk/SiSpacePointsSeedMaker_HeavyIon.h

..._xk/SiSpacePointsSeedTool_xk/SiSpacePointsSeedMaker_ITK.h

...acePointsSeedTool_xk/SiSpacePointsSeedMaker_LowMomentum.h

...SiSpacePointsSeedTool_xk/SiSpacePointsSeedMaker_Trigger.h

...acePointsSeedTool_xk/src/SiSpacePointsSeedMaker_ATLxk.cxx

...ePointsSeedTool_xk/src/SiSpacePointsSeedMaker_BeamGas.cxx

...cePointsSeedTool_xk/src/SiSpacePointsSeedMaker_Cosmic.cxx

...PointsSeedTool_xk/src/SiSpacePointsSeedMaker_HeavyIon.cxx

...SpacePointsSeedTool_xk/src/SiSpacePointsSeedMaker_ITK.cxx

...ntsSeedTool_xk/src/SiSpacePointsSeedMaker_LowMomentum.cxx

...ePointsSeedTool_xk/src/SiSpacePointsSeedMaker_Trigger.cxx