refactored repeatMoments -> repeat

In ChordDef.js, MIDIChord.js and Song Six score.
Moritz C# code has also changed:
ChordDef.Repeat is now true (=1)  by default, so
The ChordDefs in the SongSix score now always
have a repeat="0" attribute. (So that the logic
does not change in that piece.)
Bug Fix: Controls.line1818, updated scores

The scores have been updated for the new
repeat option in the palettes.
WebMIDIAPI.js is Chris Wilson's latest version
(without the delay patch). Chrome no longer
uses this shim, but needs the corresponding
option flag to be set.
Added note: activate Web-MIDI-API flag in Chrome.

Note added to top of assistantPerformer.html.
Chrome no longer uses Chris Wilson's shim!