General:
- Sound finally works! ^-^
- Code cleanup and refactoring.

Board:
- added mapper 29 (homebrew mapper for Glider);
- added mapper 50;
- added mapper 61;
- added mapper 62;
- added mapper 91;
- added mapper 148;
- added mapper 149;
- added mapper 172;
- added mapper 173;
- added mapper 188;
- added mapper 216.