Added convenience methods to MIKMIDISequence for working with the tempo track, added convenience initializer to MIKMIDITempoEvent, and changed the (double)tempo property to (Float64)bpm
Stop playback when setting the sequence, and don't set the musicSequence to NULL when stopping playback
Fixed issue with automatic stopping in MIKMIDIPlayer
Fixed issues with callback function
Made the event iterator a property