collect multislot-commands in CVWidget-classvar multiSlotOSCcmds

initialize multiSlotOSCcmds within OSCFeedback action (hence,
OSCCommands.tempIPsAndCmds should be available) but using methods rather
than making that part part of the action itself -> more modular code,
easier to debug

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