ENH: Add ability to call Visual Studio macros from CMake. Add a CMake Visual...

ENH: Add ability to call Visual Studio macros from CMake. Add a CMake Visual Studio macro to reload a solution file automatically if CMake makes changes to .sln files or .vcproj files. Add code to call the macro automatically for any running Visual Studio instances with the .sln file open at the end of the Visual Studio Generate call. Only call the macro if some .sln or .vcproj file changed during Generate. Also, add handling for REG_EXPAND_SZ type to SystemTools::ReadRegistryValue - returned string has environment variable references expanded.