Fix support for JS imports in QML files in the new compiler

Fix support for JS imports in QML files in the new compiler

Remove the v4 value initialization for imported scripts code out of the VME
(the method didn't even need any members of the VME class) and into ScriptData,
for re-use on the QmlObjectCreator side.

Also add the script index setup for the import cache (used by qml context
wrapper) to the type loader.

Change-Id: Idc3953a48f6fb66d008008e88a2b9b556c775537
Reviewed-by: Lars Knoll <lars.knoll@digia.com>