Clear all checkbox not functioning properly

[PhillipsOwen]

steps to reproduce latest problem:

start with a fresh reload of the site.
take note of the layer that is displayed
select the "check all" box, then hit the delete button
open the filter dialog
select today's date, then hit search
select a few layers, make sure you include the one that was just deleted.
click off the filter dialog and hist the "check all" button again and note that nothing happens to the one that was removed earlier.

This is related to issue #44.

[lstillwe]

All this seems to work, except Observations type of layer cards do not get checked, when selecting check all. This needs to be fixed for the March deadline

[scrummish]

@PhillipsOwen this is ready for testing on checkbox-issues branch