Sped up. +pianoRoll2matrix. Corrected midi handling.

readmidi() and writemidi() sped up about 2 times due to bitwise
operations.
added converter from piano_roll to notes.
midiInfo: silent/verbose modes.
midiInfo: corrected failure if tempo is empty.
getTempoChanges: if tempo isn't set, use default value.
piano_roll: workaround if there is zero pitch in notes.