autocomplete fix

When a prefix of a feature name is also another valid name of the same feature,
the autocomplete ranking results can suddenly change to prefer an exact match of
the shorter name over the prefix match to the longer name, e.g.
[par] -> paris, france, [phil] -> philadelphia, pa as top results
However, [pari] -> pari, france and [phila] -> phila, pa as top results
Again, [paris] -> paris, france, [philad] -> philadelphia, pa as top results

In order to fix this, ensure that prefix matches are considered alongside
exact matches during parse deduping when the best name for each feature is picked

Auditors: nsanch, blackmad