remove duplicate include in Android.mk

Signed-off-by: Wayne Wolf <wayne.ron.wu at gmail>
fix a typo that missing class keyword when defing friend class

Signed-off-by: Wayne Wolf <wayne.ron.wu at gmail>
assimp built and imported

Signed-off-by: Wayne Wolf <wayne.ron.wu at gmail>
assimp load AssetManager buffer

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