Implement an example of django admin filters

[oudeismetis]

#194 added a powerful django admin feature.
Like many features like this, there is a risk it'll never be used since the code is there but none of the out-of-the-box admin views have a filter applied.

Find (in appropriate) at least one sensible admin view that a project would have after bootstrapping that would benefit from this feature and implement it.
The feature will get a lot more use if there is a good example like that from day 1 of a project.

[franagustin]

Addressed in #232