Add the ability for users to add their own subdomains to tracker exclusion list

[Pentaphon]

Enhancement of #51

Rather than just have a hardcoded, non-user-facing list of common subdomains to exclude, I'd like to see a user-configurable list where we can add our own keywords to filter out of the tracker list to make it more readable. This will make the filter more "future-proof" and work for everybody's use-case. Ideally, the list would have the existing common subdomains already there and users can add their own keywords to the exclusion list. A good place for this is the interface tab in settings.

[qu1ck]

Added in v1.4.0