Package installation listener events.

Flesh out implementation of install session observers.  Carve out 20%
of published install progress for final system operations such as
dexopt, etc.

Add dumpsys output for active install sessions.  Create explicit
fsync() instead of overriding meaning of flush().  Hack to throw
IOExceptions over Binder calls.

Bug: 14975160, 15348430
Change-Id: I874457e40c45d2661bc0a526df9285ffea4bb77c