Database/collection support for recognizing CHD files

Recognizing CHD files in collections would be very useful. Be aware however that due to frequent bugs in chdman’s handling of CUE and subchannel data, the CHD files themselves change frequently even with the same data inside them. It may be necessary to integrate chdman in the collection scanner and build the database from the data SHA1 stored in the CHD’s metadata and avoid using the hash of the CHD file itself.