Add: shadowsocks_sysconf off/auto/global mode
Add: shadowsocksX switch Auto mode and Global mode
Add: shadowsocks_sysconf -v for detecting current version
Add: detect shadowsocks_sysconf version on startup
Update: redesign selection menu & green status bar icon for global mode.
Add: menu_icon_global.png & fix checkmark when proxy closed
remove unused comments; remember running mode when switched off, remove alert which sucks