Use entity name in saved files

Couple of small changes:

• The entity name is now used in the file name of saved .. _latest.jpg images
• The default scan_interval is 365 days, so in practice it will not scan unless you call the scan service. Alternatively you can configure a scan_interval for whatever period you like
• Some under-the-hood refactoring
• Bounding boxes are now red (rather than yellow)