Allow QuickSearch to search for civil law cases

Civil law cases in Zotero have no author or title... so, you can't cite them from the QuickFormat search box! (see issue https://github.com/zotero/zotero/issues/501).

Therefore, QuickFormat should be able to search into ```court```and ```shortTitle``` to find such items.
The commit add these two in the "quicksearch-titleCreatorYear" filter.

(Actually, it was proposed by @gracile-fr in #501; successfully implemented and tested on my dev profile.)