Add preferences.svg to plasma theme

[wuspy]

Plasma theme was missing a preferences.svg icon, which is mainly used for bluetooth status. I've modified the icon from the KArc project (https://github.com/zbeptz/KArc-theme) to work with your theme if you want it.

[varlesh]

Arc Color svg have wrong CSS and icons style:

 <style
       id="current-color-scheme"
       type="text/css">
      .ColorScheme-Text {
        color:#7B7C7E;
      }
      .ColorScheme-Background{
        color:#EFF0F1;
      }
      .ColorScheme-Highlight{
        color:#3DAEE6;
      }
      .ColorScheme-ViewText {
        color:#7B7C7E;
      }
      .ColorScheme-ViewBackground{
        color:#FCFCFC;
      }
      .ColorScheme-ViewHover {
        color:#3DAEE6;
      }
      .ColorScheme-ViewFocus{
        color:#1E92FF;
      }
      .ColorScheme-ButtonText {
        color:#7B7C7E;
      }
      .ColorScheme-ButtonBackground{
        color:#EFF0F1;
      }
      .ColorScheme-ButtonHover {
        color:#3DAEE6;
      }
      .ColorScheme-ButtonFocus{
        color:#1E92FF;
      }

Arc Dark not use CSS on svg!!!

[wuspy]

My bad, I use arc dark so I didn't even notice.

[varlesh]

No, you have wrong css and if you use fill:currentColor option color not needed.
I'm add new version