MVS board types

Some information from [HardMVS] - [HardMVS Mirror].

The number in the model name is the number of cartridge slots.

Also see ROM-Only boards.

Board naming use the following logic:
 * MVx = "Multi Video" where x stands for number of cart
 * nothing = Nec chipset
 * F = Fujitsu chipset
 * T = Toshiba board
 * S = Sharp board
 * A = Asshole (it fits so well to these boards)
 * B = because made after A
 * C = because made after B