pagination link generation repeats filter added via browser address bar

[graste]

When adding a filter to the URL of a collection the filter is repeated on the next/prev/etc pagination links

So calling

some/collection?filter%5Bstart_date%5D=range%28gte%3A2016-11-15%2Clte%3A2016-12-15%29

leads to

some/collection?filter%5Bstart_date%5D=range%28gte%3A2016-11-15%2Clte%3A2016-12-15%29&offset=300&filter%5Bstart_date%5D=range%28gte%3A2016-11-15%2Clte%3A2016-12-15%29

This is not a "problem", but should be improved.