visual issues

[dzavalishin]

• [x] start button - redraw with colored embossing
• [x] use darker BG on taskbar
• [x] taskbar height +2
• [x] toolbar icons up +2
• [x] start button up +1
• [x] weather win bg color
• [x] labels in controls got background - shouldn't - turn off default BG color?
• [x] fix window decor corners!
• [x] groups