Draft: API: remove UniqueResult, lower-case at, size for ResultSet

Summary

• Remove UniqueResult
• At and Size are lower-case now (ResultSet, MultiResultSet)

src/ccaosdb.cpp

@@ -512,8 +512,8 @@ ERROR_RETURN_CODE(GENERIC_ERROR,
                     auto *wrapped_result_set =
                       static_cast<caosdb::transaction::MultiResultSet *>(
                         result_set->wrapped_result_set);
-                    auto requested_entity = wrapped_result_set->At(index);
-                    entity->wrapped_entity = (&requested_entity);
+                    entity->wrapped_entity =
+                      wrapped_result_set->mutable_at(index);
                     return 0;
                   })
 
@@ -524,7 +524,7 @@ ERROR_RETURN_CODE(GENERIC_ERROR,
                     auto *wrapped_result_set =
                       static_cast<caosdb::transaction::MultiResultSet *>(
                         result_set->wrapped_result_set);
-                    int size(wrapped_result_set->Size());
+                    int size(wrapped_result_set->size());
                     *out = size;
                     return 0;
                   })