Add data range support in the chart.
Add save as image support to the chart.
Add auto refresh button in the chart.

But the auto refresh function is not implemented.
setInterval when auto refresh is on.
Add refresh login in route.
Add partly support for auto refresh.

Now the code is too ugly to finish auto refresh.
I have to do refactory.
Change the pb protocol to be more flexible.
Add host_id in the RegisterResponse.
Add cpu info collection in client.
Change the server to accept the new request.
Create the table in the registered stage.
Insert the stat data into db.
Show the stat in the web interface.

Use the new architecture.
Remove useless functions in db.py
Add network send and recv rate.
Add physical memory and swap memory.
Add disk IO stat.
Remove useless js code.
Get the unit from web backend.

Instead of hardcoding the unit in the web frontend,
get the unit from backend.