Add multi-finger double tap and hold gestures.

This CL includes two, three and four finger double-tap and hold.

Bug: 136131815
Test: atest GestureManifoldTest TouchExplorerTest AccessibilityGestureDetectorTest
Change-Id: I4c0a95a4ac2d13e0a7e2c7920df619063ec1cfc0
6 files changed