mv_machine_learning: add a new feature key checking function

mv_machine_learning: add a new feature key checking function

[Version] : 0.28.20
[Issue type] : bug fix

Add a new feature key checking function for machine learning based face
recognition API.

In the previous version of face recognition API, we used below key only.
http://tizen.org/feature/vision.inference.face

However, the key is used by face detection and other API - key checking
duplicated. So add a new feature key checking function so that the face
recognition API can check four keys,
	- http://tizen.org/feature/vision.inference
	- http://tizen.org/feature/vision.training
	- http://tizen.org/feature/vision.inference.face_recognition
	- http://tizen.org/feature/vision.training.face_recognition

Change-Id: I79ca9465bdec810029298323ea4c11e1ede36dee
Signed-off-by: Inki Dae <inki.dae@samsung.com>