Split joy demo into set of small services.
Split joy demo into set of small services.

All sounds are now played successively by a dedicated thread.

Change-Id: I4436549ac3913dce847e7fa5c7d69733fb1351cc

google/aiyprojects-raspbian,google/aiyprojects-raspbian,google/aiyprojects-raspbian,google/aiyprojects-raspbian,google/aiyprojects-raspbian