File manager settings

[Stoppedpuma]

This should go in preferences, the main reason I'm requesting this is for the ability to toggle specific drives from showing as the new drive detector seems to pick up virtual devices and some devices in /dev/mapper if they are encrypted with luks. This is also useful for being able to hide disks which don't have any media on them. Additionally, things such as how many threads can be used for thumbnails would work well here.