Implement the SLAndroidEffectSendItf.

Implement the SLAndroidEffectSendItf.

This enables sends from an AudioPlayer to an OutputMix
that's using the generic effect interface (SLAndroidEffectItf).
Since there is a single aux bus, the effect ID is only used
to verify the effect referred to in the send is actually
attached to the OutputMix. Also there is a single send
level value and enable flag for the interface, even though
the interface definition supports discerning between multiple
effects (so it scales on platform with multiple aux buses).

Dry (direct) level is now stored in the AudioPlayer,
as it is shared between SLEffectSendItf and
SLAndroidEffectSendItf.

Change-Id: I3dd34c4c045d8ac2961a325e10b181a789bf4913