Option for cascaded WMS Layer to respect Bounding Box of remote WMS Layer

When a GetMap request is made for a WMS Cascaded layer resource, Geoserver does not verify if the requested Map area is completely outside the native bounds of remote layer. This results in an empty call on remote server. Some services might throw exception causing the local GetMap to fail.

Hence, an improvement is proposed where user can opt for this optimization, in which when a GetMap request`s BBOX is outside WMS layer`s bounding box, the WMS Layer should be skipped.

Secondly the GUI should allow user to configure Min Max scale denominator for a cascaded wms layer also