Shared QDeclarativeEngine sidesteps GC slowdown issue.

New approach also verifies that the root object successfully loaded,
this picks up all the cases where it did not successfully load before.
Most of these were because they weren't importing QtQuick 2.0, import
statements have been updated. One was because it does not create a
QQuickItem root, it has been manually excluded. This required adding per
file exclusions to the current directory exclusions.

Change-Id: I809f0f20acc319aef58ba2e30e672e32f640686d
Reviewed-by: Martin Jones <martin.jones@nokia.com>