(PanGesture) Two motions before pan & ability to set the min distance/events via...

(PanGesture) Two motions before pan & ability to set the min distance/events via environment variable

[problem]     Need more than one motion event to determine the direction.
[cause]       N/A
[solution]    Wait at least one more pan.
              Add configurability via environment variables:
              Minimum distance before pan: DALI_PAN_MINIMUM_DISTANCE
              Minimum motion events before pan (include down): DALI_PAN_MINIMUM_EVENTS

Change-Id: I3dbe34dc56d6c84518aec3807911054280998ca5
Signed-off-by: Adeel Kazmi <adeel.kazmi@samsung.com>