Whitelist: opposite of blacklist

[Jenyyk]

Say i only want rounded corners and a nice border on a single certain window type.
Basically add on top of the existing blacklist, by being able to toggle between a blacklist and a whitelist.
You can currently have custom details for a certain window type, but not all options are available to customize. (For example border and border color)
I dont think this functionality is supported right now and it would be great.

[flexagoon]

Duplicate of #26