Hide new story link if user does not have permission to create a new story on the subproject

If a user attempts to create a story on a subproject where either:

1. The backlogs module is disabled
2. The user does not have permission to create a new story

The new dialog will still appear and a 403 error will result when the user attempts to create the story.  This change simply hides subprojects where the user does not have permission to create a new story from the drop down list.