Add typeinfo for the declarative plugin for Qt Multimedia

Add typeinfo for the declarative plugin for Qt Multimedia

For Qt Creator to correctly typecheck and auto-complete QML types and
objects, the typeinfo must be exported and added to the qmldir file.
This patch contains those changes, and an update to make updating the
typeinfo file easier in the future.

Change-Id: I988f22d3ca81839662cce4aed9d5297f7c5fbf32
Reviewed-by: Mithra Pattison <mithra.pattison@nokia.com>
Reviewed-by: Michael Goddard <michael.goddard@nokia.com>
Reviewed-by: Jonas Rabbe <jonas.rabbe@nokia.com>