cmd/stats: add timestamp info and duration option

[anysql]

Add timestamp info for each row

[anysql]

sample output:

[anysql]

Samle output:

[SandyXSD]

The dstat provides a more elegant example to control and display the timestamp, like:

$ dstat -tcdn
----system---- --total-cpu-usage-- -dsk/total- -net/total-
     time     |usr sys idl wai stl| read  writ| recv  send
17-01 14:55:19|  1   1  98   0   0|  87k  203k|   0     0
17-01 14:55:20|  0   0  99   0   0|   0   136k| 216B  792B
17-01 14:55:21|  1   0  99   0   0|   0   356k| 618B 1477B
17-01 14:55:22|  0   0 100   0   0|   0     0 | 132B  420B
17-01 14:55:23|  0   1  99   0   0|   0  4096B| 216B  488B

[anysql]

Format optimization: