desc/MIDI tutorial file needs update about \noteOnOff types

[adcxyz]

Currently, Tutorials/How_to_create_a_description_file_for_MIDI is behind the implementation:
It says \noteOnOff types has turned out problematic, it is better to make the on/off pairs by hand, or use MKtlDesc.notePair.
The current implementation has 7 tags which configure and expand elements, which simplify the creation of most mid keyboard variants - from MPadView.help :

\noteOnTrig trigger pad 127 - -
\noteOnVel trig pad w/ vel. 1-127 - -
\noteOnOff piano key w/ on vel. 1-127 0 - default
\noteOnOffBut button on/off 127 0 -
\noteOnOffVel pad/key w/ off vel. 1-127 1-127 - rare
\noteOnOffTouch pad/key w/ polytouch 1-127 0 0-127 semi-rare
\noteOnOffVelTouch pad/key w/ off vel and touch 1-127 1-127 1-127 very rare

-> this should go into Tutorials/How_to_create_a_description_file_for_MIDI as well.

[adcxyz]

started on this, but the expansion needs some more testing first anyway.