Possible memory leak in settings UI

[kostia1st]

As soon as user invokes the settings, the app consumes 10x more memory than usual.
Closing that window does not fix it.

It's yet to confirm that this is not because of tons of WPF assemblies loaded during the first settings opening.
A possible universal solution to this could be running settings in a separate AppDomain, and unloading that domain after the settings get saved.