Feat: Avatar support for carrier module

[stiartsly]

1. New APIs:
   1). Ela_get_avatar();
   2). Ela_set_avatar();
2. New callback to CarrierCallacks:
   1). onFriendAvatarChanged()
3. Internal implementation:
   1). Aavtar file
4. Update Android Java APIs
5. Update iOS APIs

[stiartsly]

Avatar support for carrier module