Optimize signal handling

Optimize signal handling

Bindings connect to lots of signals that are never emitted.  By managing
signal connection lists ourselves, we can do a much better job than Qt's
generic signal/slot connection logic.

Also, by connecting to QDeclarativeNotifierEndpoint's rather than QObject
slots, we can eliminate the need to instantiate a QObject for the V4 and
V8 binding managers.

Change-Id: I598667deaefdbd2860227bd74378a1b196761686
Reviewed-on: http://codereview.qt-project.org/6278
Reviewed-by: Aaron Kennedy <aaron.kennedy@nokia.com>
Sanity-Review: Aaron Kennedy <aaron.kennedy@nokia.com>