Publisher ID fields for Dice Multimedia, Focus Multimedia and GSP Software

[Morlit55]

These 3 budget labels use a very distinct serial format on their inserts and manuals.

Dice Multimedia
https://redump.info/disc/66853
https://redump.info/disc/33449
DCG xxxxxx or DMM xxxxxx

Focus Multimedia
https://redump.info/disc/131235
ESSxxx/D

GSP Software
https://redump.info/disc/119365
https://redump.info/disc/132107
xxxxB or xxxxA

[RibShark]

For Focus Multimedia, the serial depends on the specific label:
Essential uses ESSxxx, Revival uses REVxxx, PC Fun Club uses PFCxxx, Re:Flex uses RLXxxx

For GSP, the final letter indicates the revision (similar to # on PAL PS1/PS2) so it could potentially go to C and beyond.

[mnadareski]

I don't do any validation of the values assigned since these just end up as comment pseudo-tags at the end of the day.

[Morlit55]

For Focus Multimedia, the serial depends on the specific label: Essential uses ESSxxx, Revival uses REVxxx, PC Fun Club uses PFCxxx, Re:Flex uses RLXxxx

Forgot the later were also Focus labels. Ty