Support future dates for "Boost more recent dates" processor

PR: https://github.com/mkalkbrenner/search_api_solr/pull/87

Here is a patch version of PR 87 on github (latest commit f1cc9a7), if anyone else needs it.
PS: our setup enforces static patches and MR diffs are not allowed (as they can change unexpectedly).

I can confirm that this patch works.

And I can also confirm that the recent date processor can have weird effects on the results for future dates without this patch (and the option for future dates enabled).

Automatically closed - issue fixed for 2 weeks with no activity.