Add better statuses for network camera failures

[curtishall]

Currently we log any error as 'Not Found'. We need to support at least these two:

'Offline' (for connection timeouts)
'Authentication failed'

We also need verbose handling of errors. The actual error received from the network camera should be attached to the XML so the client can read and display it.

[curtishall]

And @abelykh

[ghost]

I propose also to display the status of camera in web UI.
@abelykh what should be the way to check if the camera is offline or otherwise failed, or not? Besides the daemon XML status request, which is currently in development? I suppose something like select * from EventsCam where device_id = $device_id and type_id = 'not found' order by id desc limit 1 ?