Reduced dependency on the Jazz plugin.

jiMain.js has been completely rewritten so that the Jazz plugin is
only responsible for setting the midiAccess object.
Plugin code for loading the available device names into the device
selectors is now replaced by new code in jiAPControls.js.
When the Web MIDI API is implemented, I can now simply replace the
call to JMB.init() by the corresponding way of setting midiAccess.

Revised the 'save' button's appearance.

Known Bug: When performing (non-assisted) with the start marker at
a position other than the beginning, message timestamps do not
take the position of the start marker into account.