T/reconcile and windows

I had two mixed bug
- on one side, when the reconcile buffer was buried, and ledger-reconcile was call again, it failed because no windows was created for it
- on the other side when the "source" buffer was saved, the refresh function could move buffer arround, and it failed when the reconcile buffer was buried.

Those two commit solve both problem, but one could argue that the reconcile buffer should be raised if buried on the second case. (It's not the case here.)