Reversegeocoding for location search

Please merge https://github.com/geoadmin/service-sphinxsearch/pull/132

Don't forget that one has to update the indices in prod for the next deploy.
https://github.com/geoadmin/mf-chsdi3/issues/844
https://github.com/geoadmin/mf-geoadmin3/blob/master/src/components/featuretree/FeaturetreeDirective.js#L206

Yeah we should change that. I left it for backward compatibility.