front: Exclude 'sectionless' config section when populating grid.
front: Remove rom lookup by crc.

No longer necessary, and adds complexity to the RomDetail interface.
front: Tweak gallery item sorting.
front: Fix possible null pointer exception.
front: Cache rom info by md5 rather than goodname.

In case the rom isn't in the database.
front: Robustify RomDetail class, return null if MD5 not in database.