Add delete() and edit() with locking to InBase

The method post_graph as not been added to InBase yet.
This is because I think it won't be used by StoredTrace.
In fact, StoredTrace provide a post_graph() via mixins:GraphPostableMixins.
If I am correct it will override the one we could provide in InBase.
Add a nosetest showing concurrency problem

When calling base.create_model() we have the following call stack:

```
-> base.create_model()
  -> base.post_graph() ** Gets a semaphore for BASE, bringing semaphore value to 0
    -> mixins.post_graph()
      -> base.ack_post()
        -> base.edit() ** Gets a semaphore for BASE, waiting for upper semaphore to release
```

We see that a semaphore for BASE is needed multiple times in these encapsulated call. Making it impossible to proceed.