Add "howto" link to scan-throttling message

[sirtet]

On first startup, a howto was shown on how to deactivate throttling.
It would be nice if there was a way to open this howto from the place(s) where the warning (see screenshot) is shown

[VREMSoftwareDevelopment]

Currently the links to How-To, FAQ and other URLs are available on the Application About page.