Overhaul the Visual Studio 2008 Projects

Overhaul the Visual Studio 2008 Projects by using property sheets to
consolidate commonly-used items, so that projects can refer to them, which
will help to simplify future maintenance, and move all the projects to
MSVC_Net2008/.

	* MSVC_Net2008/atkmm-build-defines.vsprops:
	* MSVC_Net2008/atkmm-version-paths.vsprops: Added property sheet
	  files used to consolidate commonly-used items to be referred to
	  from the projects.
	* MSVC_Net2008/gendef/gendef.vcproj:
	* MSVC_Net2008/atkmm/atkmm.vcproj: Move to MSVC_Net2008/, and
	  clean up by using the property sheets.  Adjust the source file
	  paths accordingly.
	* MSVC_Net2008/atkmm.sln:
	* MSVC_Net2008/filelist.am: Adjust file paths accordingly.