Add possibility to hide "panel spy"

"Collapsable" enables the possibility to collapse a panel using "collapse" parameter in the dashboard configuration.

I just did the same : "spyable" enable the possibility to "spy" a panel. By setting spyable "true", the "panel spy" part of the editor is hide.

Because something you want to allow edition but not spy. With these changes, it will not be possible to enable spy through the editor.