Add demos for using support-dynamic-animation lib

This project contains two demos:
1) A single spring that reacts to user gestures:
   The spring can stretch when it gets pulled
   with user drag gesture. when user lets go of
   the spring, it will return to equilibrium.

2) A set of springs chained together. When user
   moves the first view, the subsequent views that
   are attached to the moving view with springs will
   then start moving.

In both of these demos, users can tune the spring
constants via the seek bars.

Test: ./gradlew support-animation-demos:assemble

Change-Id: Ibea58d5110dc345221a7c366567ad5a7bef5563b
20 files changed