Compilation changes

Few compile time attempts to speed things up

Swap include guards for pramga once
Change compile options in the cmakeLists for source
generate a pch

small tweaks

Engine/source/core/virtualMountSystem.h

@@ -19,6 +19,7 @@
 // FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 // IN THE SOFTWARE.
 //-----------------------------------------------------------------------------
+#pragma once 
 #ifndef _CORE_VMS_H_
 #define _CORE_VMS_H_