Cleaned up menu-bar icons to closer resemble the dock icon and have more consistent colours with Apple's menu-bar icons. Also added HiDPI variants - Refs #15931
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
