improve ApparatusCriticusSearchView for multiple OTs

[acholyn]

The search view works fine with one original text but if an instance has multiple original texts, this stops working. We could filter it by OTs that have ApCrit items and combine the results

[acholyn]

double check that this isn't an issue when adding new apcrit items

[tcouch]

See https://www.ucl.ac.uk/history/frrant/fragment/51/ for example