utxos by asset add policy id filtering

[ecioppettini]

With these changes any of the following are valid:

curl -X "POST" "http://localhost:3000/asset/utxos" \
     -H 'Content-Type: application/json; charset=utf-8' \
     -d $'{
  "fingerprints": ["asset1c43p68zwjezc7f6w4w9qkhkwv9ppwz0f7c3amw"],
  "range": { "minSlot": 22505578, "maxSlot": 22515578 }
}'

curl -X "POST" "http://localhost:3000/asset/utxos" \
     -H 'Content-Type: application/json; charset=utf-8' \
     -d $'{
  "policyIds": ["919d4c2c9455016289341b1a14dedf697687af31751170d56a31466e"],
  "range": { "minSlot": 22505578, "maxSlot": 22515578 }
}'

curl -X "POST" "http://localhost:3000/asset/utxos" \
     -H 'Content-Type: application/json; charset=utf-8' \
     -d $'{
  "policyIds": ["919d4c2c9455016289341b1a14dedf697687af31751170d56a31466e"],
  "fingerprints": ["asset1dgp85pz2m6pcs43jmkdy0fctngm56s9xd9kleg"],
  "range": { "minSlot": 35939453, "maxSlot": 35939853 }
}'

Also the policy id and asset name are added to the output, so that it's possible to index by policy id, for example. The fingerprint could be computed from those, but it's kept anyway to avoid that extra step.