data transfer demo

1. use MicoCloudService lib v0.1.1;
2. transparent transfer(unformat package, raw data):
MCU <==> Cloud;
3. with simple control cmd(format package) from USART:
Packet format: BB 00 CMD(2B) Status(2B) datalen(2B) data(x) checksum(2B)
wifi module reset:               BB000900000001000139FF
wifi module reset default:   BB0009000000010002xxxx
wifi module power down:   BB0009000000010003xxxx
start Easylink:                      BB0009000000010005xxxx
start cloud service:             BB0009000000010006xxxx
stop cloud service:             BB0009000000010007xxxx
get status:                          BB000800000000003CFF

NOTE: xxxx is checksum(2B, little-ending)