highlight submit system button

[qjiang002]

This PR is related to issue #516

If the user hasn't logged in, they will see System page like this. The tooltip is default visible. User can click either 'Log in' button or 'Submit New System' button to log in.

If the user has logged in, they will see System page like this.

[lyuyangh]

Thanks, @qjiang002 !

I like how you made the "New" button more visible by making it bigger. I think we should maybe reserve danger (red) buttons for operations that are risky and less frequently used (e.g. delete) though. This is also what antd suggests (doc). WDYT?

[qjiang002]

Thanks @lyuyangh . I change the color to 'call-to-action' (green) as suggested in the doc.

[lyuyangh]

Looks great!

[neubig]

Thanks!