add wavefront loader

start adding various scenes to test gpu rigid body pipeline
reserve more memory for shapes (concave triangle mesh can be huge) in GLInstancingRenderer
fix a few crashes when 0 objects

demo/ObjLoader/string_extra.h

@@ -0,0 +1,8 @@
+#ifndef STRING_EXTRA_H
+#define STRING_EXTRA_H
+
+char strequal(const char *s1, const char *s2);
+char contains(const char *haystack, const char *needle);
+
+
+#endif