Maize Sampler 2.03 update

[caoxiang]

- Added custom knob and button widget supports in player XML
- Fixed a bug in release trigger
- Fixed a bug in MIDI CC group selection
- Updated documentation


Button: button node shows a rectangle button on screen. You can change the appearance by specifying "normalcolor", "overcolor" and "downcolor". The default normal color is transparent, so the button image can be put in the background. The possible actions are about, instrumentlist, grouplist, nextinstrument, previousinstrument. You can also set the action value as a URL string. When the button is clicked, the player will open the system browser with that URL. For example: <Button x="10" y ="10" action="http://www.maizesoft.cn" />

Knob: New in version 2.03 for custom knob, you can leave the knob background as a part of the player background, and then specify the "dot" as parameter name and the dot size as value. For example, <Knob x = "10" y = "10" action = "volume" dot = "4" min = "-30" x = "6"> will create a custom knob which only draws a dot as current angle.

The restriction of same vendor for instrument and player is also removed.

[caoxiang]

Hot fix uploaded. Please update.