SoundTriggerMiddlewareService logging decorator

Rigorous logging of all SoundTriggerMiddlewareService interactions.
This implements logging as a decorator and removes the ad-hoc logging
done inside the implementation.

This gives us a centralized place to handle
SoundTriggerMiddlewareService events. We're planning to do more than
just write these to the log eventually.

Change-Id: I510ee3073095cca78ec0b9c5ff876610225d002f
Merged-In: I510ee3073095cca78ec0b9c5ff876610225d002f
Bug: 150325756