ndi.fun.channelname2prefixnumber

  CHANNELNAME2PREFIXNUMBER - identify the prefix, number from channel name string

  [PREFIX, NUMBER] = CHANNELNAME2PREFIXNUMBER(CHANNELNAME)

  Given a channel name like 'ai5', return the prefix (in this case 'ai') 
  and the number (in this case, 5) as PREFIX and NUMBER, respectively.

  Example:
   [prefix,number] = ndi.fun.channelname2prefixnumber('ai5')
    % prefix == 'ai', number == 5