VT: Postpone bitrate down for considering camera switch

1. If received packet is too few, it has a possibility that opponent switches camera
   For that possibility postpone bitrate down for 3 seconds.
2. A thread class form a concept of timer is implemented.
   These are introduced to support QualManager's timer operations like (1.)
3. License message added

Merged-in: I6b69cbb555eec99bf45dc77ba5e24affdbcd3776
Change-Id: I6b69cbb555eec99bf45dc77ba5e24affdbcd3776
Signed-off-by: Kim Sungyeon <sy85.kim@samsung.com>