Support both UDP and TCP and use UDP in the first place

[cn-members]

Current Situation
Users from many regions of china suffers connectivity issues using BTS wallet, while having no problem using other softwares including p2p softwares supporting udp. We think it is because network roubustness in many areas in china is not enough for long term TCP connection.



Suggestion
Support udp and choose udp firstly in BTS wallet and thus increase connectivity