Updated cmake to better organize folders and options.

This adds solution folders that properly group gtest/glslang/hlsl.
This also marks gtest options as advanced so they don't show up
in cmake-gui by default.

OGLCompilersDLL/CMakeLists.txt

@@ -1,6 +1,7 @@
 set(SOURCES InitializeDll.cpp InitializeDll.h)
 
 add_library(OGLCompiler STATIC ${SOURCES})
+set_property(TARGET OGLCompiler PROPERTY FOLDER glslang)
 
 if(WIN32)
     source_group("Source" FILES ${SOURCES})