Support for secondary group of proxy
This commit add supports for secondary group of proxy This way, a proxy can now be listed from another group like this :
<ProxyGroup name="new_group">
< Proxy group = "group" name ="proxyname" />
</ProxyGroup>
Enabling easier dynamic list of proxy in proxy list domain
It also uses this feature with the StreamTracer. A Side effect of this is, the order of proxies in a ProxyListDomain being alphabetical, that the default StreamTracer seed is now HighResLineSource.