Implement socks5 support

This adds following settings:

- Socks5Enabled
- Socks5Host
- Socks5Port
- Socks5User
- Socks5Password

Currently http requests and dns requests are not getting executed as they currently can't get tunneled through socks5 proxy. Therefore gmail with oauth2 wont work through tor.

src/config.rs

@@ -48,6 +48,12 @@ pub enum Config {
     SmtpCertificateChecks,
     ServerFlags,
 
+    Socks5Enabled,
+    Socks5Host,
+    Socks5Port,
+    Socks5User,
+    Socks5Password,
+
     Displayname,
     Selfstatus,
     Selfavatar,