Add option to list executables that are allowed to run during silent update

In the beginning of a silent update the updater checks that executables in the install directory are not running - except the maintenance tool, of course. Sometimes there is a need for other executables to continue running too. Therefore it would be nice if those executables could be defined in the configuration such that the updater doesn't ask to stop them. The same way as it doesn't ask to stop maintenance tool.