also update log format

[TBASE-1047] Go connector prints all the SQL. This will harm the performance and consume unnecessary hard disk space. Modified to print only the SQLs which returns error.

format the code

- Fixed bug when the least significant bits of timestamp may cause time to be converted to 0
- Fixed small display bug with time and sig figs.

这个dbname都没有传进行，在连接池的情况下，每个连接都在选 use db.

当连接池切换连接时，就会出现 invalid DB。
```
8/16 12:44:46 dsn.go:59: input dsn: root:taosdata@/tcp(127.0.0.1)/sensors_test
TAOS DRIVER 2019/08/16 12:44:46 dsn.go:130: cfg info: &{user:root passwd:taosdata net:/tcp addr:127.0.0.1 port:0 dbName:sensors_test params:map[] loc:0xed6be0 columnsWithAlias:false interpolateParams:true parseTime:true}
TAOS DRIVER 2019/08/16 12:44:46 taosSqlCgo.go:52: taosQuery() input sql:INSERT INTO d_BDCF682B78F44364AA551B0F5E6BD1F6_acc USING acc_data TAGS ('BDCF682B78F44364AA551B0F5E6BD1F6','20190816-
TAOS DRIVER 2019/08/16 12:44:46 taosSqlCgo.go:61: taos_query() failed: invalid DB
```

Subscription implemented
Continuous Query implemented
Fixed bugs when dealing with null values retrieved from tables
Removed unused code
Added basic performance test code

Bug fix

removed broken code