Add a alert panel when not all value sets are available

Currently, we can see the status of the individual value set but if some are unavaible and not shown (because not listed on the first page), it is not obvious to the administrator that something is not correctly configured.
When at least one value set is not reachable, display a red alert above the table to notice the administrator of such failure.
Optionnaly add a green display when all value sets are reachable.