Improve 4k Monitor usability.

1) When using a 4k orUHD monitor on mint, you have to go and switch to auto user interface scaling under settings->general. It would be more friendly to move this option to settings->display and to enable it by default due to the high usage of varying sizes of UHF and 4k monitors.

2) The DPI autoscaling scales things annoyingly large in my personal opinion, and this will of course vary between users. Windows fixes that by letting users choose from a variety of scaling percentages, but linux mint only allows for double or auto scaling. Adding this would again make using 4k monitors friendlier to the average user, which is important for how ubiquitous they'll become in a few years.