Feature request: Let admins specify which columns are shown/hidden by default

[edenhaus]

With #1058 we got the possibility to hide columns and since the commit dd8fa5ff66a3533dba00a191d299564f9c35d6db this settings will be stored by user on the server.

I think it would be great, that the admin has a possibility to set which columns are shown/hidden per default. The button is only visible if the current user has enough rights and my idea was to add another button next to the OK one.

[berrnd]

On the other hand the method public function GetUserSetting($userId, $settingKey) in UsersService.php will return the default settings if no user ones are specified and default one exists.

Please keep it to one topic per request, keeping track of things is hard otherwise - I've splitted that into #1169 (and also consider this a bug, thanks for testing).