Add filters to repository statistics view

[lukasjelonek]

The main goal of the repository statistics page is to provide answers to the question What is inside bakrep?.

To add additional value to the page it might be an option to add filters that select only a subset of the available datapoints that are plotted, e.g show only the genera that contain the substring Escherichia.
This would allow for a personal look into the composition of the bakrep dataset on genus and species level.

@oschwengers Is this something we should add?