Implemented b3OpenCLUtils::setCachePath

Also made kernel caching work on Mac OSX (and likely Linux, needs testing before enabling)

Demos3/GpuDemos/main_opengl3core.cpp

@@ -409,6 +409,8 @@ void myprintf(const char* msg)
 
 int main(int argc, char* argv[])
 {
+	b3OpenCLUtils::setCachePath("/Users/erwincoumans/develop/mycache");
+	
 	b3SetCustomPrintfFunc(myprintf);
 	b3Vector3 test(1,2,3);
 	test.x = 1;