Allow cli options

[ghost]

It would be nice to have some basic cli options.

Off the top of my head, it would be cool to have features like this included in the cli options.

Colorless flag option
Pick and choose widgets

[aksakalli]

another idea is to show/hide certain panels #16

[erviker]

network interface and disk also need CLI option so that one can choose what interface and what disk to monitor

[bulletmark]

I installed gtop to see what it was like. First thing I typed was gtop -h and then gtop --help but in both cases it just started without any output/complaint which I have to say is somewhat off-putting. All Linux CLI programs should provide this.