mv_machine_learning: separate object detection group

mv_machine_learning: separate object detection group

[Issue type] : code refactoring

This is a code refactoring patch to separate existing object detection group
into two groups - object detection and object detection 3d groups.

We cannot combine these two groups with one because each group has default
model so in the use case that user uses object detection and object detection
3d model API together, one of them isn't allowed for the use.

So separate them into object detection and object detection 3d groups.
As for the object detection group, this patch provides only skeleton code
for mobilenet ssd model.

Change-Id: I97737ce07a07398a510e1f508608a8bdf24844cc
Signed-off-by: Inki Dae <inki.dae@samsung.com>