OctaMED .MED-file loading support

[MBeijer]

To-do:

• MMD0 / MMD1 loading
• MMD2+ loading
• Sample loading

[MBeijer]

To-fix:

• MED-files using BPM instead of SPD gets the wrong speed
• Transposed instruments/samples gets way more transposed than it should
• MIDI/Synthesis/Hybrid instruments causes weird behavior (crashes, sample sounds not playing)