Proxy names specified in 'start' params divided by ',' will be started. If it is empty or not defined, all proxies will be started.
if login_fail_exit is false, when frpc first login to server failed, it will continues relogin to server every 30 seconds.
support udp type
Conflicts: src/frp/cmd/frpc/control.go src/frp/cmd/frps/control.go src/frp/models/config/config.go src/frp/models/server/server.go