Webui: Enable live agent log scrolling

Having too much logs is cumbersome which could be improved by allowing scrolling logs.

vestbo: One thing to look for is if any of the other CI systems out there have the log browser as a standalone JS component that we can re-use:

https://stackify.com/top-continuous-integration-tools/

https://www.google.no/search?q=cloud+ci+tools+list&oq=cloud+ci+tools+list