Add Filelight menu to Tools menu

Add Filelight menu to Tools menu

The menu for installing and launching Filelight was only available
through the status bar free space info button until now. By default
we do no longer show the free space info button because the status
bar has been changed to show less information by default.

This commit adds the "Manage Disk Space Usage" menu to the "Tools"
menu in the menu bar so it is more discoverable for users.