NativeApp is stored in as weak_ptr in AppContext

Signed-off-by: Wayne Wolf <wayne.ron.wu at gmail>
fix matrix stack push crash

fix crash when calling top() on empty stack, by inserting an identity
matrix on matrix stack beforehand.

Signed-off-by: Wayne Wolf <wayne.ron.wu at gmail>
trivial change

Signed-off-by: Wayne Wolf <wayne.ron.wu at gmail>
ndk_helper vectmath replaced by glm-0.9.5.4

Signed-off-by: Wayne Wolf <wayne.ron.wu at gmail>
remove a camera in cube_triangulate model

Signed-off-by: Wayne Wolf <wayne.ron.wu at gmail>
use aspect from app, not from model

Signed-off-by: Wayne Wolf <wayne.ron.wu at gmail>