Some way to indicate when no layers satisfy current filters

[almccon]

For example, Canada has no Pre-planning areas. Should there be a message that is displayed when there are no layers on the map?

Or, perhaps there should always be a running total of how many layers fit the current filters?

[almccon]

Perhaps this should involve reviving the layers list in some form. See #34

[danrademacher]

We just discussed adding simple counts within the status filters, like this:

Vary based on whether ALL, US, or CANADA is selected, but not by map zoom.

[sconnelley]