servicemanager: Add listen service to the service table

- Listen is a voice activation feature.
- When an application registers a "keyword" with
  ListenService, then events are sent to application
  when that keywork is spoken by user and detected
  by ListenEngine.
- ListenService runs within the MediaServer process.
  The ListenService needs to be added to service table
  in order for application thread to have permission
  to access Listen functionality.

Change-Id: I8c79bebc92920d0b62b12ef925cb35a59644ee86
Revert "remove support for glReadPixels screenshot path"

This reverts commit 3ca76f416bc8665a97636ca8a2d0128b9da9d92c.
Support forcing all screenshots into a CPU consumer

Looks like a full GPU path is less efficient on some GPU
drivers that we're still using, and CPU is reliably faster...
(there's probably a locking condition going on somewhere, this
needs to be looked into)

Change-Id: I8878796a117d65bf2324507cf8755cadce49f6dc