deere: use deck colors for waveform zoom controls background

changes the waveform zoom control buttons at the right end of the main
waveforms to match the deck color scheme:

- background now uses deck-specific color (blue/orange/violet/lime)
- icons changed from white (#d2d2d2) to black (#000000) for better
  contrast against the colored backgrounds

files modified:
- deck_waveform.xml: added deckbackgroundcolor to waveformzoomcontainer
- icon/ic_add_48px.svg: changed fill to black
- icon/ic_clear_48px.svg: changed fill to black
- icon/ic_remove_48px.svg: changed fill to black

Author: Milkii Brewster

res/skins/Deere/deck_waveform.xml

@@ -134,6 +134,7 @@
         <ObjectName>WaveformZoomContainer</ObjectName>
         <Layout>vertical</Layout>
         <SizePolicy>min,min</SizePolicy>
+        <BgColor><Variable name="DeckBackgroundColor"/></BgColor>
         <Children>
           <Template src="skin:left_1state_button.xml">
             <SetVariable name="TooltipId">waveform_zoom_down</SetVariable>

res/skins/Deere/icon/ic_add_48px.svg

@@ -960,7 +960,6 @@ WOverview #PassthroughLabel {
 }
 
 #WaveformZoomContainer {
-  background-color: #333333;
   padding: 1px;
   qproperty-layoutSpacing: 2;
 }