add a optional 'cnt' argument for benchmark cmd

we can do this:
./bin/deploy.py cluster0 nbench 100

[ticket: X]
backup rdb files after the dump

what happened

[ticket: X]
change path of statlog

xxx

[ticket: X]
change back... put cluster info in the json line
small change on monitor
add history cmd, modify live_xxx cmd names

xxx

[ticket: X]
modify some config numbers

modify @ online  cluster

[ticket: X]
do log rotate of nutcracker

- statlog move to data/cluster-name/statlog.xxxxxx
- add log_rotate and upgrade_nutcracker task

[ticket: X]
history add a "cnt" argument
add cgi web server
add cgi/index.py
online change