CVWidgetMS: set the multi-slider's reference accordingly if the spec has zero-crossing

Signed-off-by: nuss <st9fan@gmail.com>
- CVWidgetMSEditor: fix focus when the editor gets sent to front from within a CVWidgetMS
- CVWidgetEditor, CVWidgetMSEditor: fix label string-colors when switching to a different tab

Signed-off-by: nuss <st9fan@gmail.com>
add the TabbedView for MIDI to CVWidgetMSEditor

Signed-off-by: nuss <st9fan@gmail.com>