Allow to configure trash storage location

[sptcguy]

A super helpful feature for larger deployments would be the ability to change the storage location for the trash. I'd like to store my users trash on a separate block device and utilize VDO. This way I can make more efficient usage of my storage.

For deployments that use SSD backed storages, such a feature would also allow for cheaper, HDD storage to be used for trashed items instead.

Just like there's a "datadirectory" attribute, it'd be great if we could set a "trashdirectory" attribute.