Overhaul the Visual Studio 2008 Projects

Split up the property sheets used to build JSON-GLib, and make all the
projects (*.vcproj) and property sheets (*.vsprops) use UNIX line endings
to simplify future maintenance.  Also add projects to build and "install"
the json-glib-validate and json-glib-format tools.

Move the introspection file generation out of the Visual Studio projects
to add an NMake Makefile later to generate the introspection files, to make
the process clearer to people.

Stop installing the test programs, although they continue to be built from
the projects for now.

Similar changes to the Visual Studio 2010 projects will follow.