add Wechat SPP demo

1. add Wechat SPP demo using EasyCloud;
2. change Airkiss timeout to 60s, connect AP timeout to 30s;
3. fix Airkiss CM3 static lib.

NOTE:
1. use Airkiss to config device(connect AP);
2. send && recv message from wechat client:
     wechat   <===>  dev(USART)