The function currentProject() returns the current project based
on the current project node.
If the current document was newly created by a wizard, this did not work.
We use SessionManager::projectForFile() as a fallback.

For Qt Creator 3.2 we plan to unify this functionality with die Qml
code model.

Change-Id: I296224671a0b496fbf6fd0d8e62e74c28b4f9abb
Reviewed-by: Marco Bubke <marco.bubke@digia.com>