Add QProperty to WPushButton for whether the widget is pressed.
Add QProperty to WWidget for the widget value and disabled state.
Add <Text> node for each WPushButton <State>. Allows push-buttons without pixmaps.
Link MIDI input/output ports that have have "in" in the input port and "out" in the output port.
Allow WPushButton to be styled with a style sheet.
Allow WSliderComposed to be styled with a style sheet.
Allow WStatusLight, WDisplay and WKnob to be styled with a style sheet.
Remove duplicate method.
Ensure that audio connections for decks > 2 will succeed on startup.
Merge pull request #134 from ywwg/4deck-audio-input-fix

Ensure that audio connections for decks > 2 will succeed on startup.
Merge remote-tracking branch 'upstream/master'